First tell yourself what sort of man you want to be; then act accordingly in all you do. For in almost everything else we see this to be the practice. Athletes first determine what kind of athlete they want to be, and then act accordingly. … You will find the same in the arts. If you are a carpenter, you will have these procedures, if a blacksmith, those. For, if we do not refer each of our actions to some standard, we shall be acting at random; if to an improper standard, we shall fail utterly.

~ Epictetus