When to Stick with Something and When to Quit

Here’s a simple heuristic that has been monumental for me:

If you love something you don’t need any reasons for doing it.  If you hate something you’d better have damn good reasons for doing it.

This is about the burden of proof. If you’re doing what you love and what makes you come alive, you don’t need any justifications or elaborate arguments or cost.
Sure, you might find something you love even more if you keep an open mind, but you’re more likely to find that by diving headlong into what’s working without looking back.
If, on the other hand, you’re dull, listless, feeling a bit dead inside, you’d better start asking why you haven’t quit what you’re doing.  You’d better discover good reasons and fast.
My life motto is, “Don’t do stuff you hate.”
The only exception is when something you hate meets two conditions: 1) You know it will get you to something you love, and 2) You know there is no other, better way to get there.  I hated running but wanted to be someone who’d run a marathon.  The training sucked, but it met both criteria.  I knew it would make me able to finish the race and I knew there was no other, better way.
It’s rare for something you hate to meet both of these criteria.  It takes a lot of self-knowledge and self-honesty to really discover if it does.  It’s much easier to just keep doing stuff that doesn’t make you come alive because you don’t want to risk the worry or disapproval of others.  But that’s not any kind of life to live.
So, if you’re loving something don’t feel pressure to prove or explain yourself to the world.  Stay alive!  But if you’re bored and unhappy with something, you’d better start asking questions quickly.  If you can’t definitively prove it will get you someplace you know you want to go and that nothing else would, stop right now.  Quit as soon as possible.  Exit.  Keep exiting until you’re not doing stuff you hate.
There’s no virtue in hope if it’s an aimless, indefinite hope that continuing with a job/school/relationship/life you hate will somehow magically result in something you don’t.  It won’t.