No, you are a truly awesome guy. I speak from experience when I say that self-depreciation only makes the situation worse.
(Forgive the use of a video game example here, I can't help it) In a Halo multiplayer match, you have to believe you can, regardless of your abilities. Believe you can capture the flag. Believe you can maintain control of the hill. Believe you can get that headshot. If you don't believe those things, you won't be able to succeed. If you don't believe you can capture the flag, you won't be able to get it back to your base. If you don't believe you can maintain control of the hill, it'll be taken by the enemy team. If you don't believe you can get the headshot, you'll end up getting headshot yourself.
The same thing applies here: if you don't believe you're what people say you are, you won't be able to pull out of your depression. Don't beat yourself up. It only makes things worse.