The Bowl of Saki Commentary

We need not escape pains and pangs; these must be, so long as we carry a mind. But mind is not the abode of understanding, heart is the abode of understanding. Trouble will not cease with the opening of the eye of the heart, but the evanescent character of disturbance will make itself clear. So time alone is sometimes a healer.

Exercising a muscle may cause a pain or overworking a muscle may cause a pain, but the first kind of pain makes no impression on the personality because there is a purpose in it. It is in this sense, when there is a purpose in view, that every burden is as a load in exercise, and the pain does not cause anguish.