when your instructor gets out...
I'd hope it would happen before then!
How about
- first complete flight without instructor input
- first spin
- first launch failure or engine failure
- when everything just "goes right"
- when the instructor gives you an unexpected "now get out of that situation", and you do
after that lot, first solo
should be an anticlimax.
BTW don't be disheartened when (not if) you've been improving, and then it feels like you're making negative progress. It happens to most people.
Also, I'd try different instructors on principle - you'll learn different things from each of them.