In Daryle Hoole's book, one of her daughters who suffered from severe depression, said that she made a personal first aid kit for her "down days." In the kit she included scriptures, her journal, favorite talks, quotes, phone numbers of people who she knew could cheer her up or of people she knew might need some cheering up, and she included good music.
I thought this was a really good idea because on those days that you are down it is so hard to remember any good and it would be nice to have it all right there to remind you. You could also include a gratitude journal. My husband would always ask me on the days I was down what I was grateful for. It would take me a while to come up with something other than the standard answers but I could eventually get going (if I wasn't being too stubborn that is). It is very helpful to have reminders of what you are grateful for when you are in such a fog that you can't see clearly.