There is a famous saying: "If the mind is not contrived, it is spontaneously blissful, just as water, when not agitated, is by nature transparent and clear." I often compare the mind in meditation to a jar of muddy water: The more we leave the water without interfering or stirring it, the more the particles of dirt will sink to the bottom, letting the natural clarity of the water shine through. The very nature of the mind is such that if you only leave it in its unaltered and natural state, it will find its true nature, which is bliss and clarity. So take care not to impose anything on the mind, or to tax it. When you meditate there should be no effort to control, and no attempt to be peaceful. Don't be overly solemn or feel that you are taking part in some special ritual; let go even of the idea that you are meditating. Let your body remain as it is, and your breath as you find it. Think of yourself as the sky, holding the whole universe.
--Sogyal Rinpoche, in The Tibetan Book of Living and Dying from Everyday Mind, edited by Jean Smith, a Tricycle book