It's not something that you can just simply ignore. Getting ride of true depression is quite hard, honestly. It won't just go away on it's own.
If you're suffering from clinical depression, or bipolar depression, I suggest that you talk to your parents or a doctor about it.
However, if you're experiencing casual depression, like we all do sometimes, I'm going to tell you that happiness is a choice. It doesn't just fall on you. Focus on the good things, hun. Breathe in the sunshine and look around at the people who love you. Do things that cause you to feel relaxation. Maybe talk a walk or talk to a friend. Sadness doesn't last forever, I know, I've been there a few too many times :) x