“There are very few things in the mind that eat up as much energy as worry. It is one of the most difficult things not to worry about anything.
Worry is experienced when things go wrong, and in relation to past happenings it is idle merely to wish that they might have been otherwise. The frozen past is what it is, and no amount of worrying is going to make it other than what it has been. Nonetheless, the limited ego-mind identifies itself with its past, gets entangled with it, and keeps alive the pangs of frustrated desires. Thus worry continues to grow into the mental life of a person until the ego-mind is burdened by the past.
Worry is also experienced in relation to the future, when this future is expected to be disagreeable in some way. In this case worry seeks to justify itself as a necessary part of the attempt to prepare for coping with the anticipated situations. But things can never be helped merely by worrying. Besides, many of the things that are anticipated never happen; or if they do occur, they turn out to be much more acceptable than they were expected to be. Worry is the product of feverish imagination working under the stimulus of desires. It is the living through of sufferings that are mostly of one’s own creation.
Worry has never done anyone any good; and it is very much worse than mere dissipation of energy, for it substantially curtails the joy and fullness of life.”
– Discourses 7th Ed. p 357