Know when to keep on trying and when to give up. Sometimes it's just better for yourself to let it go. Contrary to what many appear to think, admitting you reached your limits doesn't make you weak. Everyone has their limits. After all no matter how many amazing things we do and create, we're still humans and there's nothing wrong with that.
I know the whole "work/study/try harder and you'll do it. Never give up and you'll do it". I like that motivation, but at the same time, with all due respect, I'll call bullshit on that. That's giving false hopes to the people who won't be able to do it no matter how hard they try, and with that make them think there's something wrong with them, when in fact that's just how thing go. Not everyone is the same. Not everyone will have the same abilities. The idea that just because one did it, then everyone is capable of doing the same sometimes is just wishful thinking.