Some people have different things that can inspire them greatly in times of depression. If you have certain things that can make you feel better, why not write them out and place those papers around your home. This way you can see these inspiring thoughts at all times.
You need to remember that everyone has bad days. No matter who they are and how much money they have. A person will never in their life be happy all the time. It's not normal, and you can't ever expect it. That's why you need to remember inspiring thoughts at these low times.
Perhaps you have a favorite book that you enjoy many quotes from, maybe even the Bible. Even if you're not a very religious person there are some very good inspiring comments in the Bible that everyone can enjoy.
Think of something you've accomplished in the past. Be it a simple thing like a story you wrote or a poem even. Though it may never have been published when shared with friends they really enjoyed it. This should inspire you to perhaps even write another one, and get you out of that mood.
Movies that you always find that make you happy can have some inspiring thoughts in them to make you feel less down too. Placing that movie on and watching it, or just the scenes that always make you laugh or smile can be enough of a push to bring you from a down mood to an up mood.
Finally, you need to keep in mind that you are no different from anyone else. We all experience these feelings of being down. Just don't let them get too bad before you seek out a friend to talk too. If you ever get close to thinking of hurting yourself call your best friend up and chat, they will help you out.