Give it time. It will come back. You’ve put your body through the wringer the past year and I would expect it to take another year to get half way back to where you were when you did the E ridge of Temple (really good time by the way, that’s a challenging climb for route finding). At our age major trauma like this takes a much bigger toll than 30 years ago. I’d suggest dialing back the ago meter a bit too. More years like this and you might no recover.
Most of your body’s energy has been going into healing this past year. Now that you know that this recent hike was too much, dial back to 1/2 that for a few hikes till those become easy. Overdoing it will not be the most effective way to rebuild your body and it’ll take a big mental toll. Set smaller, more achievable and regular goals.
It really is going to be more about your mind than your body. Your body will get fitter but you need to not be hard on yourself. In my long history of coaching I have found that I and the those I do much better with positive reinforcement as opposed to negative.
Good luck and keep us posted.