pleasure is very strong motivation.
food with fat in it tastes good to us because it has high energy content, which was essential to hunters and gatherers who couldn't get much food. it's nature's way of rewarding them.
sex is pleasurable because it's nature's way of rewarding procreation. if it didn't feel good, who would do it?
gambling is pleasurable because you get the chance to gain something without having to work for it. sure, you might lose all you have, but that doesn't register in the face of immediate results.
this is why miracle diet pills and exercise machines don't go out of business.
at the end of the day, we are all hedonists who live for pleasure. we might suffer in the long run, but then and again, we might not wake up tomorrow either.
whether we play it safe, go crazy, or find our personal balance in between, it depends on a mix of biological and environmental factors. some of us are wired to seek pleasure more than others. some of us are brought up to deny ourselves pleasure more than others.
that's all there really is to it.