I assume many people on here do.
For me personally, this is often about certain chord changes I not only dreamt up there and then but even got out of my fingers - something I knew I couldn't do but then did inexplicably.
There were other moments too that take too many words, but the most stellar moment was the day I played a Bach piece on the pipe organ, and exactly that day I played better, deeper and with more musical expression than I've done before or after. It became very hard to even finish the piece, and I was exhausted.
That was not the moment.
The moment was: unbeknownst to me, a young soprano had entered, and rather than making herself known she'd waited and listened before approaching me. When the piece was done, she came up and said:
- "You know, I've always hated the pipe organ, but you just explained it to me."