For me, the issues have been mostly one of endurance. Even when i was in really bad shape, but still attempting to work 5hrs a week or so, my colleagues said, "you're still super sharp." but those calls/work would utterly wipe me out.

My endurance is a bit better now so after really taking about two months off (ok, i worked about 10hrs in 2 months) i'm starting back 5-8 hrs a week next week. My boss has been great and is going to start me on just focusing on two projects rather than taking back over management of my team. They got jerked around a lot when i kept trying to return to work then had to quit again (like 6 times), so she's being cautious about my return, which works in my favor. I'll do 5-8hrs/wk as long as i need to until i feel i can handle more without impacting my rate of recovery.

Good luck. I guess my advice is to start back as gradually as possible. Biting off more than you can chew is bad for everyone, especially you.