Would you say you are putting a great deal of pressure upon yourself to accomplish things? Are perhaps the goals and standards you set for yourself too high? Are you the type of person to do tasks because you don't trust someone else doing them as well as you would?

These are what immediately comes to mind.

If this is close to what is happening my suggestion would be to set some smaller goals. Oh they can still be lofty but a smaller goal may mean only looking at one task at a time. Delegate some of the work to others. If this is hard to do then help but try to avoid doing it all yourself. And adjust your expectations and standards. Ask yourself maybe if these are realistic? Are they the same standards someone in the same position would expect?

Just some thoughts coming at me. if I am nowhere near the ballpark, my apologies.