After I play through a program or a piece for someone (as a step in preparing for public performance), I don’t return to the piano to practice. It can be difficult, if something went badly and I want to work on it. But the separation — practicing for the real concert by preserving the “non-take-twoness” of the performing experience — matters most.
I’ve read of Busoni returning to the hall to play through an entire concert after the audience departed. For me, it seems a bad idea, a misunderstanding. What has “gone wrong” in a performance, what doesn’t satisfy the player, frequently doesn’t result from lack of practicing or lack of physical skill. Problems arrise from a lack of readiness for the encounter with the heightened awareness, the fluttering stomach, the frisson of the concert.
I can get ready more reliably by drawing a frame around my playing, previewing the once-and-only-once mindset of the concert. And as I don’t play after run-throughs, I also do not play for 30 minutes before run-throughs.
I take the sometimes bitter pill and do not touch the piano.