Another idea I've been keeping to mind is becoming okay with not being the best / immaculate at things that you do. For example, at work I check certain details over and over again, but all too often I get hard on myself when I still manage to leave something out. It's actually impossible to do everything right all the time, but we often make ourselves an exception to that rule. Plus-- a lot of practice goes a long way in looking out for errors. Be good to yourself. You will remember next time.
Also, I starting to become okay with realizing I'm not good at certain things and someone else is much better for the job. This isn't to say striving for the best is over rated. It's just to say striving for the best shouldn't glorify feeling miserable. There are plenty of things that are worth your hardship and lend positively to your sense of self.