People say you should never give up

All over social media people talk about how you should never give up on someone who hasn’t given up on you. That you’d be dumb to let someone like that go...

But what if I’m not happy? And it’s been 3 years and nothing has changed? Would i still be stupid to give up on him when he’s stuck around when I’ve left him before AND cheated? I’m not happy... but i don’t wanna make a mistake