Greg,
I agree with bcbcbc55 finding an outlet that takes you thoughts away from the "broken record" is probably the best way to help change the feelings you are having.
A good book either reading in a quiet place or listening to one on cd or mp3 player while walking in a park have helped me get though these bouts.
Even going to a museum, not for the exhibits but try this, go on a Saturday or Sunday if time allows and watch the looks of wonder the children have for the place. Watch the smiles and remeber when...
Good luck to you and keep smiling it makes people wonder what you've been up to!
JPQuigley