By all accounts I've heard, there will always be performance anxiety. Actually, I think the more time you put into the music and the better you get, the more fear you will feel on stage because there's that much more at stake. Having a trainwreck hurts less if you're a bumbling beginner than if you know you're better.
Here's an exercise I found useful s1d1f1 (assuming you've already practiced the piece to the best of your abilities): Before you walk into your practice room pretend that you're about to go on the stage. Imagine the audience, the building (helps if you can see the place beforehand), you walk up to the piano, sit down and get comfortable. Look at the keys and imagine "this is a piano that I'm unfamiliar with and I'm not sure how it will react", all eyes are on you and you only have one chance to play through the piece, there can be no stopping and making corrections now... aaaaand begin.
The idea is to experience the stage fright and practice under those conditions, imagine it as real as possible until you really feel the butterflies and nervousness. What you're practicing is to be able to play through mistakes without letting them spiral into other mistakes, how to avoid anticipating problems (which has the tendancy to create problems), to listen carefully as you begin a piece and adapt to an unfamiliar piano.
I practiced like this 3 times once the night before a performance and by the time I had to play I was feeling much more comfortable and the playing came out better than I expected.