Enjoy Yourself while Playing...
I have had some trouble with this hint, specifically with recitals with a more or less masochistic background. With such a background you are not allowed to enjoy things, isn't it? Even if you are not masochistic, overreacted self criticism will bring little enjoyment either.
Fortunately I remember one recital full of enjoyment: the first "Concert with Candlelight" we (Hans and me) played in Delden, many years ago.
There it was, sheer enjoyment and pleasure on stage. The result? You notice how beautifully the Inventions of Bach are composed and how well the parts sound together. You notice how helpful the acoustics of the beautiful old church can be for the breathing in an Aria by Johann Adolf Hasse. And the most surprising: I cannot remember any fatal faults in the performance on that specific occasion. In this way you have enjoyed your musical performance as least as much as the audience did.
So that is very important: ENJOY yourself while playing music!
Just one caveat: If you are playing before an audience you're not there for yourself alone. So don't let your enjoyment distract you too much!