I always get really nervous the first time I perform a piece. So I always make sure that my main performance is like the 5th or 6th time I've played it in front of someone. If possible, I try to have a mock performance at a retirement home very close to the big performance date, so there are lots of people there, and they can't even hear if I make mistakes because they are so old. They also tell me how good I was no matter how well I played, which gives me a heightened sense of confidence. If I do that, then I usually end up being fine. The down side to playing at a retirement home is they will most likely bake you some type of cookie that you will not like. You will have to come up with an excuse for why you can't eat the cookies. I usually tell them I'm allergic to cookies, and they usually believe me. In general though, play in front of as many people as possible as many times as possible.
And as for specific tricky sections, as you get up to the big performance date, you will have to trust your preparation. I would practice those sections very slowly, trying not to make any mistakes, and I would practice those sections a lot. If for the last week you have practiced the sections slowly, without making any mistakes, you might trick yourself into forgetting that those sections ever presented any problems to you at all. Good luck!