While depression is certainly miserable, it may be caused by pessimism... Pessimism and depression what a combo! HOWEVER, the person who is depressed and a pessimist might make a very good Editor... depressed ppl tend to correctly assess situations and things and not allow too much fluff (go figure.)

I suggest a book that IF you read and follow, WILL help you if you really want things ( and your outlook) to change: Learned Optimism by Dr Martin EP Seliger.