How do I know if I'm sad or depressed?

Depression feels very different from sadness. Every person witnesses and sees sadness in their life. Depression is a mood disorder, which can be diagnosed. Some describe it as a feeling like you are worthless. It is on a much higher scale than sadness and can do much more damage. If you do ever feel like you are worthless or this life just isn't for you, please talk to a friend, parent, doctor, or a listener on this site. It will help, a lot. Even if you feel in the beginning, that you are all alone in this situation, there is always someone who can relate to you.