Everyone gets down on themselves at one time or another. All you need to do is talk to your true friends. Hell, sometimes I get into really depressive moods and my obsessive list-taking takes over... I end up writing a list of all the reasons I hate myself. And you know what? There is always a friend, and I'm sure it's the same with you, that will tell you that those reasons are BS. That only yourself hates you for those reasons, nobody else.
Write a list down. Show one of your true friends. Listen to what they have to say. Then keep that list. Wait until you're in a really good mood. Look at the list. You'll realise just how stupid some of those reasons are. It's natural for when we're down to kick ourselves. Rise above that. Don't listen to what the little, annoying people in your life have to say about you. That'll bring you down. Then you'll start kicking yourself.