Morals - all correct moral laws - derive from the instinct to survive. Moral behavior is survival behavior above the individual level.
Robert A. HeinleinNote the individual and subjective nature of each case. No two are alike and there is no reason to expect them to be. Each man or woman must find for himself or herself that occupation in which hard work and long hours make him or her happy. Contrariwise, if you are looking for shorter hours and longer vacations and early retirement, you are in the wrong job. Perhaps you need to take up bank robbing. Or geeking in a sideshow. Or even politics.
Robert A. HeinleinAround the time of the Terran Caesar Augustus, a Martian artist had been composing a work of art. It could have been called a poem, a musical opus, or a philosophical treatise; it was a series of emotions arranged in tragic, logical necessity. Since it could be experienced by a human only in the sense in which a man blind from birth might have a sunset explained to him, it does not matter which category it be assigned.
Robert A. Heinlein