When we consider meditation, we cannot stress too much the importance of having the right reasons for taking it up. Meditation — or, as a better translation of samadhi, collectedness — is only one aspect of Buddhist practice, and must, to be successful, go hand in hand with such other practices as generosity, gentleness, nonviolence, patience, contentment and humility. If such genuine qualities of the Dhamma neither exist in oneself initially, nor grow through one's practice, then something is drastically wrong, and only a foolhardy person will try to proceed. The practice of collectedness is based upon firm roots of virtue (sila) and cannot succeed in anyone who does not make a real effort to be strict in keeping the precepts.http://www.accesstoinsight.org/lib/auth ... el116.html
Interesting TMingyur.Thanks for contributing.And here some dangers of meditation and some signs too
There have, for instance, been those who took up meditation as a way to invest themselves with power, so that they could easily sway or hypnotize disciples. Others have seen it as a quick way to gain both disciples and riches. Fame may also be an unworthy motive. All these, as motives for playing with meditation, may easily lead the unwary into illness, and sometimes mental unbalance. There is nothing worse in Buddhist meditation, where a person's own sure experience is of paramount importance, than a half-baked disciple who sets himself up as a master.
This obviously leads on to a further danger — that of pride, of which there are several forms. One such is the pride of the person who has seen manifestations of light during meditation, and supposes this to be the sign preceding mental absorption. Then there is the pride of one who touches on a mental absorption if only for an instant and as a result assumes that he has become a Noble One, and this can be a very powerful factor in convincing himself if not others. Quite ordinary people who take up meditation may beware of the common "holier-than-thou" attitudes: "I make an effort, whereas you . . .," or, "I meditate every day, whereas you . . ." Pride is a great obstacle to any progress, and while it is only a Buddha or arahant who is entirely rid of it, everyone should have the mindfulness to check it.
Related to this is the danger for the person who always looks for so-called progress. He is sure that he is making "progress" because in meditation he sees lights, hears sounds, or feels strange sensations. He becomes more and more fascinated by these as time goes by, and gradually forgets that he started with the aspiration to find the way to Enlightenment. His "meditation" then degenerates into visions and strange happenings, leading him into the realms of occultism and magic. There is no surer way for a meditator to become entangled than this way. Fascinating though all such manifestations may be, they should be rigorously cut down by resorting to bare attention, never permitting discursive thought regarding them, and thus avoiding these distractions.
Among "visions" which one may see, whether they be internal (produced from one's own mind) or external (produced by other beings), there may be for some meditators an experience of the fearful, such as the sight of one's own body reduced to bones or inflated as a rotting corpse. If such an experience occurs, or others of a similar nature, one should withdraw the mind from the vision immediately, supposing that one has no teacher. Visions of the fearful variety which occur to some people may be very useful if rightly employed, but without a teacher's guidance they should be avoided.
Another danger is trying to meditate while one is still too emotionally insecure, unbalanced or immature. An understanding of the value of meritorious deeds or skillfulness will come in useful here. As merit purifies the mind, it will be an excellent basis for mind-development, and both the ease with which absorptions are gained and the ease with which insight arises are to some extent dependent upon merit. Meritorious deeds are not difficult to find in life. They are the core of a good Buddhist life: giving and generosity, undertaking the precepts, help and service to others, reverence, listening whole-heartedly to Dhamma, setting upright one's understanding of Dhamma — all these and more are meritorious deeds which bring happiness and emotional maturity. Merit, one should always remember, opens doors everywhere. It makes possible, it makes opportunities. To have a mind at all times set upon making merit, is to have a mind that may be trained to develop absorptions and insight.
Obviously it follows that to try to practice meditation while all the time retaining one's old cravings, likes and dislikes is, to say the least, making one's path difficult if not dangerous. Meditation implies renunciation, and no practice will be successful unless one is at least prepared to make efforts to restrain greed and hatred, check lust, and understand when delusion is clouding the heart. How far one carries renunciation and whether this involves outward changes (such as becoming a monk or nun), depends much on a person and his circumstances, but one thing is sure: inward renunciation, an attitude of giving-up with regard to both unskillful mental events and bodily indulgence, is absolutely essential.
Often connected with the above dangers is another, to be seen in cases where a man suddenly has an opportunity to undertake a longer period of meditation practice. He sits down with the firm resolve, "Now I shall meditate," but though his energy is ever so great and though he sits and sits and walks and walks, still his mind is disturbed and without peace. It may well be that his own strong effort has much to do with his distractions. Moreover, he has to learn that it is necessary to meditate knowing the limitations of his character. Just as any other worker who knows the limits of his strength and is careful not to exhaust himself, so is the able meditator careful. With mindfulness one should know what are the extremes, of laziness and of strain, to be avoided.
It is through straining or forcing meditation practice that many emotionally disturbed states arise. Sudden bursts of intense anger all over insignificant trifles, fierce cravings and lusts, strange delusions and even more peculiar fantasies can all be produced from unwisely arduous practice.http://www.accesstoinsight.org/lib/auth ... el116.html