This a a reminder to not fall victim to the sunk-cost fallacy. Just because you invested time and energy into something, does not mean you should indefinitely waste more time and energy on it, if you decide it’s not what you want anymore. This goes for anything, from books, to relationships, to jobs, to hobbies, etc.
If it’s not serving you anymore, move on.
This is honestly one of the places I find Marie Kondo's advice most helpful. I stop, look at the thing I've spent time and money on only to realize I dislike, and I say, "Thank you for teaching me something about myself and my preferences. I think I've learned this particular lesson and we can part ways now."
And then I don't feel like I "wasted" things or made a mistake. I just tried one path of learning about myself, learned something, and now it's time for a different path. Works a lot better for my brain.