There is so much popular misinformation in people's minds about what contemplation is.  Saying what ist is not may help to put a perspective on what it is.

The first thing contemplation is not is a relaxation exercise.  It may bring relaxation, but that is strictly a side effect.  It is primarily relationship, hence, intentionality.  It is not a technique,, it is prayer.  When we say, "Let us pray", we mean, "Let us enter into a relationship with God", or, "Let us deepen the relationship we have".  or, "Let us exercise our relationship with God".  contemplative prayer is moving our developing relationship with God to the level of pure faith.  Pure fait is faith that is moving beyond the mental egoic level of discursive meditation and particular acts to the intuitive level of contemplation.  It is not to get "high" such as you may get obtaining by ingesting Peyote or LSD.  It is not a form of selp-hypnosis.  It is simply contemplative prayer.
The second thing that contemplative prayer is not is a charismatic gift.  The charisms enumerated by Paul have been renewed in our time.  These gifts are designed for the building up of the community.  One may be a contemplative and a charismatic at the same time.  And one may not be a contemplative and still have one or more of the charismatic gifts  In other words, there is not necessarily a connection between the two.  Contemplative prayer depends on the growth of faith, hope, and divine love, and deals with the purification, healing and sanctification of the substance of the soul and its faculties.  The chrismatic gifts are given for the building up of the local community and may be given to people who are not necessarily advanced in the spiritual journey.  The gift of tongues is the one gift that may be given primarily for one'x personal sanctification.  it is a kind of introduction to contemplative prayer because, when praying in tongues one does not know what one is saying. 
Another gift is the ability to communicate the experience of resting in the Spirit.  If you have already had some experience of contemplation, you would recognize it as the gift of infused recollection of perhaps even the prayer of quiet.  You can resist it if you santo to.  If you accept it, you fel a mild suspensin of your ordinary sense faculties and you slip to the floor.  If people have never experienced this kind of prayer before, they go down with great delight and stay down as long as they can.
Apart from the gift of tongues, the charismatic gifts are clearly given for the good of others.  They include the interpretation of tongues, prophecy, healing, administration, the word of wisdo, and inspired teaching.  Prophecy can exist in people who are not holy at all.  A classical example is the prophet Balaam, who prophesied what the King wanted to hear rather than what God had commaned him to say.  Charismatic gifts are frequent in our time and people tend to get excited about them, it is important to realize that they are not an indication either of holiness of of an advanced stage of prayer.  They are not the same as conteplative prayer and do not automatically sanctify the people who have them.  On the contrary, if one is attached to them, they are a hindrance to one's spiritual development.  Even in the exercise of charismatic gifts, emotional programming is a work.  According to Catholic tradition, the straight and narrow path of contemplative prayer is the surest and safest path to holiness.  The charismatic gifts are accidental or secondary to that path.  Obviously, if one has such gifts, one has tointegrate them into one's spiritual journey.  But if one doesn't have them, there is no reason to think that one is not progressing.  The process of transofmation depends on the growth of faith, hope, and divine love.  
Contemplative prayer is the fruit of that growth and furthers it.  Right now the charimatic renewals is in great need of the traditional teaching of the Chur on contemplative prayer, so that charismatic prayer groups may move on to a new dimension in their relationship with hte Holy Spirity.  They should introduce periods of silence into the prayer meetings so that shared prayer becomes grounded in the practice of interior silence and contemplation.
The third thing that contemplative prayer is not is parapsychological phenomena such as precognition, knowledge of events at a distance, control over bodily processes such as heartbeat and breathing, out-of-body experiences, levitation, and other extraordinary sensory or psychologic phenomena.  The psychic level of consciousness is one level above the mental egoic stage, which is the general level of present human development.
In any case, psychic phenoma are like the frosting on a cake and we cannot survive on frosting alone.  We should not overestimate psychic gifts, therefore, or think that holiness manifests itself in extraordinary psychic phenoena.  Such manifestations, including levitation, locutions, and visions of various kinds, have been sensation in the lives of some of the saints.  Teresa of Avila and John of the Cross, for example, had these experiences.  The Christian tradition has consistently counseled avoiding extraordinary gifts whenever possible because it is difficult to remain humble when you have them.  Experience teaches that the more extraordinary the gifts, the harder is to be detached from them.  It is easy to take secret satisfaction in the fact that God is giving you special gifts, especially when they are obvious to others.
There are actually methods to develop direct control over physiological functions like our breath, heartbeat, and body temperature.
Unsual physiological or psychic powers appear to be innate human capacities that can be developed by practicing certain disciplines.  But they have nothing to do with holiness or the grouwth of our relationship with God.  To regard them as a sign of great spiritual develpment is a mistake.
The fourth thing contemplation is not is a mystical phenomena.  By mystical phenomena, I mean bodily ecstasy, external and internal visions, external words, words spoken in the imagination and words impressed upon soul.  John of the Cross in the Ascent to Mt. Carmel cosiders every conceivable spiritual phenomenon from the most exterior to the most interior and commands his disciples to reject them all.  Pure faith, according to him, is the promate means of union with God.
External visions and voices can be misunderstood.   Even saints have misunderstood what God has said to them.  Divine communications of an intelligible kind have to be filtrred through the human psyche and one's cultural conditioning.  In those who are led by this path, such communications are probably authentic eighty per cent of the time but inauthentic the other twenty per cent.  Since one can nevr tell which percentage group a particular communication belongs to, if one follows these communications without discretion, one can get into all kinds of trouble.  There is no guarantee that any particular communicaton to an individual is actually coming from God.  Even if ti is, it is almost certain to be distorted by one's imagination, preconceived ideas or emotional programming, any one of which can modify our subtly change the communication.
All the sacraments are greater than any vision.  this is not to say that visions may not have a purpose in our lives, but as John of the Cross teaches, a genuine communication from God accomplishes its purpose instantly.  Reflecting on it does not make it any better - but often distors it - by losing its original clarity.  This does not prevent one from mentioning it to a prudent spirtual director to make sure one does not take it too seriously or to lightly.  If one is told by God to do something, it is especially important not to do anything without fitst discerning the matter carefully with an experienced spiritual director.
Much more reliable than visions, locutions, or the process of reasoning are the inner impressions that the Spirit suggets in prayer and to which we feel gently but consistently inclined.  The more important the event, the more we have to listen to sound reason and consult a spiritual director.  God's will is not always easy to discern; we have to observe all the indications of it and then decide.  Int the struggle for certitude however, we perceive more clearly what the obstacles are in ourselves to recognizing His will
We come now to the question of mystical graces.  They are the hardest to distringuish becaus ethey are so intertwined with our psyche.  By mystical ggraces I mean the inflowing of God's presence in our faculties or the radiance of His presence when it spontaneously overtakes us.  The levels of mystical prayer have been well described by Teresa of Avila and John of the Cross.  They include infused recollection, the prayer of quet, the prayer of union, the prayer of full union, and finally, the tranforming union.
Here are people who have given their whole lives to the service of Christ and yet have not internal assurance of having had even the least mystical grace.  I am convinced that it is a mistake to identify the experience of contemplative prayer with contemplative prayer itself, which trascends any impression of God's radiating or inflowing presence.  The essence of mysticism is the path of pure faith.  Pure faith, according to John of the Cross, is a ray of darkness to the soul.  There is no faculty that can perceive it. One can be having this "experience" on the deepest level beyond the power of any faculty to perceive it.  One can only remark its presence by its fruits in one's life.  God can be beaming that ray of darkness into someone who is faithful to prayer without his or her being conscious of it at all.  In any case, THE PEOPLE WHO HAVE THE MOST EXUBERANT MYSTICAL LIVES ARE MARRIED OR IN THE ACTIVE MINISTRY.  Perhaps God does not give this consolations to the cloistered folks in the same way because He has decided that they have enough support from the structures of their enclosed lifestyle.
What is the essence of contemplative prayer? the way of pure faith.  Nothing else.  You do not have to feel it, but you have to practice it.