I saw a thing the other day. It was an interview with Stephen Fry. He described his experiences with mental health problems, and he used an analogy that I think as a really good one.
Depression is like weather in your head. Sometimes it's raining, and you have to remember that it won't rain forever. You can't stop it raining right now, but just remember that it doesn't rain all the time.
I'm not one for motivational quotes, but this one really struck a chord me!