A GM I worked for asked me one time, "Why are you stressed?".  I replied that I want to get it done correctly.  I said, "I don't want to fail."

He looked at me funny and said, "What's the problem about failing?"

I guess it was because at school you received a sticker & a tick for getting it right. 
When you got it wrong, there were no stickers or ticks, just disappointment from the teacher.

His rationale was, "You know what you're doing.  That's why I employed you.  And I know, that if you didn't know, then you'll keep at it, until you do know.