[This is a revised version of a comment I made on a locked post, because I realized I'd said something that I, personally, needed to hear--and probably need to hear on a regular basis.]
The fact of failure isn't what matters. Because that's just going to happen. Unless you choose to stop trying. What matters is that you pick yourself up, literally or metaphorically or both, and go on, and the next time you fail, you try to fail differently.
Now, I am the first person to admit that I am very bad at practicing what I preach, here. I went through my entire education on the understanding that anything less than perfection was failure, and failure was . . . it was the apocalypse. I think, in retrospect, it would have been good for me to get a C or two in college, just to force me to realize that it wasn't the end of my academic career, or of me as a worthwhile person, or whatever the hell I thought it would be. Yes, I finished my doctorate with a perfect 4.0. All that it has gained me is that I have anxiety dreams about fucking up my GPA. Still. Even though I know that GPA means nothing, that no one cares. I don't even care. But I have the anxiety dreams all the same.
But my point is, if you don't fail, or don't allow yourself to fail, you don't become a better person. You become a more rigid person. More brittle. More uptight. And because you don't allow yourself to fail, you have no empathy for other people when they fail. You don't have room for it, because you can't give yourself the leeway to imagine failing.
So failing--or coming short of what you're aiming for--or just making a mistake--totally sucks. But that's not because it means you are a bad person or a stupid person or a useless person. It sucks because it hurts and it's hard and because it leaves you vulnerable. But I still have to believe it's better than the alternative. I used to have a sign taped to my monitor (before I got the sleek new flat panel) that said Perfection is death, and maybe I should find somewhere to post that again.