Life isn't perfect, but you can't have ups without downs. Remember that feeling down is part of feeling human. Maybe you've lost somebody you care about, or maybe you've lost yourself, but don't stay tied to the things that hurt you. Turn to the light, take some time and try to understand that you have so many things to be thankful for, even something as simple as the sun in the sky, and the wind in the trees.
Life is a gift.