it depends on the game. there are some games that I will never really stop playing, even if I take long breaks. for others, if I lose interest partway through the story, I either move on or set it aside for another go in the future... assuming I still think it's worth playing.
I just go with what I want to play (or sometimes what I want to want to play, if it's not what I typically go for). I deal with enough rules and pressures in my life to add yet another thing to the list.
we have such a limited amount of precious time on earth. why would you waste it on something that has practically no benefit except for a number on a screen?