When you're depressed you may constantly remind yourself of everything negative you do and everything negative that happens around you. It's a lousy habit, but a persistent one.
It seems only fair, then, to acknowledge the positive things that happen, too.
Make a list.
Did you stick to your diet today? Run errands? Clean out your emails? Spend quality time with family? Do the dishes? Refill your prescriptions? Do your online banking? Take much needed time to do nothing?
Then today was a good day!