"high-performance knowledge worker that places a lot of self-worth in the quality of his work "
I have a very similar story to yours and it took me a few years to figure this out. You may have to learn to accept a lower level of performance from yourself. You may need to accept that you can't put out the type of quality that you used to, and at the speed you used to. Burn out is _serious_ and it can drag you down a pretty dark path. Beating yourself up over not being who you know you are will make things a lot worse. It isn't easy to do, but it also isn't permanent. It's better to let things go for a while (maybe even a year or two) until you are in a place mentally where you can handle the load of your own expectations (in combination with the load of all the different stressors in your life).
Move slowly and accept a long timeline for recovery. I'm finding that it is still quite easy to slip back into burnout if I push too hard. Spend time working on basic self care. Are you sleeping well? Are you eating healthy food? Are there any chronic health concerns that you could take this time to address? Are you depressed? Consuming too much alcohol? You might find that the way back starts with just taking care of yourself, and doing what you can to shield yourself from internal and external stressors.
"I plan and I scheme"
Before I started to recover I had a list of all the things that I expected myself to do. I even broke it down into the quarters of the year that I expected to achieve things by. That list, and the consequences of planning and self expectation had nearly terminal consequences. Consider that, and be gentle with your own expectations. I still record my ideas and the things that I want to do, but they aren't actionable. They'll still be waiting for me when I'm ready.