Have you ever played Tetris?
If you’re one of the three people on Earth unfamiliar with this game, you have to line up clusters of squares in such a way that they eliminate themselves by forming a complete line from one end of the screen to the other, while more (often of the incorrect shape for what you need) fall from the top with increasing rapidity. You play until you aren’t fast enough, and you lose.
You can’t win.
There’s no victory condition. You just play until you can’t any more. Your goal is to lose slower. The better you get at Tetris? Your reward is just that you get to play more Tetris.
There are traps like that in life just lurking all over the place. Things you can do whose only reward is to get better at that thing, maybe do more of it, but the “it” isn’t that great to begin with. I don’t mean to bash Tetris if you love it as a pass-time or something, but at least with Tetris you know it’s a meaningless distraction. Other things in your life act a lot like that, but without the cool music and flashing lights to let you know that you’re playing a game that you should stop at some point.
Other things you can waste your whole life doing like that.
If you really like doing something, go ahead and spend your whole life doing it. But come up for air every once in a while and ask yourself if you actually really like what you’re doing. It’s okay to stop if you don’t. And if you’re doing something for the sake of some other value it can give you – money, skill at a related but separate task, prestige, etc. – then make sure you set yourself a limit where you say “when I get to this point, I’ll have done this enough to be okay with quitting since I don’t really enjoy the thing in itself.”
You don’t always need the high score at everything. You can go for a personal best, or you can play the game for fun, or you can use it to learn. Sometimes more than one. But don’t just line up the blocks for the sake of it. They all disappear anyway.