All negativity is caused by an accumulation of psychological time and denial of the present. Unease, anxiety, tension, stress, worry - all forms of fear - are caused by too much future, andnot enough presence. Guilt, regret, resentment, grievances, sadness, bitterness, and all formsof nonforgiveness are caused by too much past, and not enough presence.

Eckhart Tolle

from The Power of Now: A Guide to Spiritual Enlightenment