If you look at yourself in your moments of pleasure or pain, you will invariably find that it is not the thing in itself that is pleasant or painful, but the situation of which it is a part. Pleasure lies in the relationship between the enjoyer and the enjoyed. And the essence of it is acceptance. Whatever may be the situation, if it is acceptable, it is pleasant. If it is not acceptable, it is painful. What makes it acceptable is not important; the cause may be physical, or psychological, or untraceable; acceptance is the decisive factor. Obversely, suffering is due to nonacceptance.
(Source: I Am That, 59. Desire and Fear: Self-centred States)
Know Thyself 