Just a quick observation, mostly for my own benefit:
I need to eliminate the sentence "But I used to be able to do this posture!" from my brain.
Just do the posture, already!!
Observation without judgment, without attachment. It's a big idea, and it's the main reason I got interested in this yoga in the first place. And judgment comes from expectations, right? Better to let those go and just do some good yoga. The postures come, then go, and then come back again. Just try, and don't do it wrong, and try again! At the end of the day, the postures don't matter and there is plenty of time.