It is OK to quit
If you're undertaking a task that takes up a lot of time and effort, are you staying with it because you (a) enjoy the process, (b) really want the outcome, or (c) just because you started it, so you feel you can't quit.
As a middle-aged person, I've come to realize that "a" and "b" make sense -- but "c" typically isn't worth it.
As an example: you've invested hundreds of hours on a carving a huge sculpture. If you enjoy the process of carving, then it's "a": keep going. If you're tired of carving -- but you think the final product will be really great (or: it's on commission, and you need the money) -- then it's "b": it's about the outcome.
But, "c": it sucks, and you don't care about the outcome any more -- but you hate to be a Quitter? Eh. Cut your losses. Life is short, and you only get a certain number of hours. Go do something better with your time -- or at least re-frame the project so that you can salvage something useful out of what you've done thus far.
I remember quitting the wrestling team in 9th grade, about three weeks into the practice season, because it was taking up SOOO much time and I just wasn't enjoying it. The coach said that I should "stick it out" at least through that season, and I'd regret it if I quit. Nope! I quit, never looked back, and NEVER regretted it.
I intended the above as a guideline for hobbies -- but it would also work for occupations
BTW -- "b: the outcome is important" includes "helping other people". For example, if you're volunteering at a soup kitchen and you find it boring -- but you think the work you're doing is important -- then yeah, keep on going.
Finally: the image a the top of this post? A planing stop. Bad pun.