One of the best performance enhancer (formerly known as dealing with performance anxiety) tips I know is:
Focus on Preparation and Effort. Spend your time working on what is under your control: your preparation and effort.
(The above tip is from an article I wrote on the ideas of legendary UCLA basketball coach John Wooden, http://www.clarinetmike.com/docs/Wooden_and_Music_Tips_Online.pdf)
For example, in getting ready for an upcoming recital, I should focus completely on preparing the music and myself to the best of my ability. And then when it is time to actually perform, I need to focus totally on “going for it,” i.e. my effort at the moment of performance.
Also, as I perform I need to stay “in the moment,” intent on my effort and not become distracted by how good or bad I’m playing – I especially must NOT think about what others might be thinking. Further, as I perform I need to calmly and immediately accept what happens and quickly forget about it while performing. There will be time for reflection and analysis later. (“What did I learn today?” is always a good question to ask after a recital, master class, lecture, etc.)
I have found John Wooden’s ideas on success (his definition and famous Pyramid of Success) to be very helpful in this area: http://www.coachwooden.com/index2.html.