There comes a time where everyone has to just call it quits, stop being whatever they have been for the better part of their lives and move on, or settle down, or just find something to do for the last years of one's life. As the case may be.
For others, such time comes much earlier, as there are lines of work that are much more draining on one's personal health, patience and ability to function properly. Adventurers usually spring to mind first, for it is known to the better part of the populace that their life expectancy is really not all that high, and most of those "retired adventurers" survived because they quit early.
Actually, "quit while you're winning" does not just apply to gambling, as many such people can testify. However, there are those that did not quit while they were winning, and thus started losing; for those that are lucky enough to still have their life, even quitting late would be better than nothing. "Life to fight another day", they also said.
And then, there are those for whom the mere act of quitting equates to losing one's life.