A change in the own attitude about the experience of sharing music could help to reduce nerves. I’m not saying it’s your case, but, if we’re playing piano to impress someone, or to receive applauses and the admiration of people, nervess will appear. The first thing is to have clear our intimate purpose for playing piano, since the will of our heart determines the kind of thoughts we have.
Let us be sure that our main motivation for playing piano is our love for the music. So, share the music not your abilities. Avoid thoughts such as “let impress them with my fast arpeggios”, or “what a shame if I forget the piece”, since they reveal that one is too much concentrated about oneself, and worried about the impression one makes on others.
It would be better to cultivate a new music-centered attitude, thinking for example “let me show them how great these Bach’s harmonies sound” or “let us hear how touching is this passage”. In doing so we are deflecting our attention from ourselves and directing it towards the composer’s work, and therefore managing to reduce our nerves. In other words, let the music shine and use us instead of using the music for our own shine. Music is the actual star, not the player.