Hey Hey,
I used to be the same way. I could do it all right, meet the deadline, everyone was happy, goal met!!
But then after I always crashed. Really down mentally and physically like you said.
My only way to deal with it is to have a job that never slowed down.....you can see where this goes right? But then before I got too burnt out I ended up moving to Norway and let me tell you, it's been tough not having a good, challenging job. But, as hard as it has been it has taught me some valuable lessons.
I dont think anything I have said helps now except maybe that I understand. I was forced to change my ways. I hope someone else can help with some ways to avoid the crash.
Heidu

Every path to a new understanding begins in confusion- Mason Cooley