How different would childhood had been if we had to wait until a painting was perfect before showing it to anyone?
Did anyone care if we colored outside the lines?
When we misspelled something at five years old, it was cute most of the time...right?
Yet when it comes to music, we tend to get preoccupied with making sure everything is perfect. Notes, rhythms, nuance, everything.
But, it's all the same with skill acquisition. We want our kids to do their best, but they will (and should) make mistakes. It's all part of the process. It's their version of scribbling and misspelling.
If it's not quite ready, perform it anyway. If it feels like something's going to go wrong, do it anyway.
Then do it again.
Rinse and repeat.
Being messy and proud of it is how the real learning gets done.