Daily affirmations are a good way to pick yourself up. We all have bad days and you can't always count on other people to make things better. So for your own ego you need daily affirmations.
Some obvious affirmations are: "I am a good person" or "I love myself" or "I matter." But I think it's a good idea to start small. You should say things that make you feel good because they are easy to accomplish. ("I will wake up." "I will brush my teeth.") Don't push yourself.
The more depressed you are, the simpler the affirmation should be. Under the right circumstances, "Who cares if I'm drunk?" is a perfectly reasonable affirmation!