I've pretty much been doom and gloom my whole life, aside from mania where i'm THE top of the world. When depressed i dont "feel" that there are positives in my life. Sometimes I take it to the extreme and convince myself that anything positive I may have felt in the past is a delusion. Talk about delusional!!
Trying to manage depression with bp has been challenging. The depression doesn't take as strong a hold of me as it used too since I've alwaus come out of it eventually. I have a couple depression mantras:
i keep telling myself "this too shall pass; its only an episode."
" Feelings aren't facts"
"its ok, i get like this sometimes"

I also schedule "sheet therapy" days during a depression once a week and on the other 6 days I force myself to go to work, eat and go outside for at least 5 minutes and take a shower/brush my teeth etc.