If you accept the premise that training cycles are the method by which you will improve your climbing, you should be able to focus less on the day-by-day fluctuation in your performance. At least, I should be able to, since I accept that premise. Yet I still struggle to not be moderately disappointed if I don't perform as I hope. The antidote is thus:
Build a plan. Evaluate success on how hard that plan pushes you, while still being possible. Then follow that plan.
I missed the mark in a recent session because I couldn't put together a plan that was challenging and possible. One or the other was easy, but I couldn't get both.
My goal was a ten-move sequence on a systems board that was very challenging, but could be barely be done repeatedly with 60 seconds of rest between attempts.