Are you your own worst enemy?

If somebody did the things to me i've done to myself, i'd kill 'em.

I am most ceartianly my own worst enemy. Not just because it's a catchy saying.... I really am.

Deep breath, friend! It's all going to be okay.
I assume you have at least one friend, and probably many. If you don't, think about what you're learned from books and movies.
Would a friend speak to you the way you talk to yourself? Would a friend hurt you and put you down and criticize you and never let you be good enough?
Not a real friend, no.
Try to treat yourself like you would a friend. When you have a nasty thought to yourself, stop and say, "No, that's not fair. It's okay that I failed/That really was a success." It sounds goofy, but after a while it starts to work.
I really strongly suggest that you seek some counseling for this problem, because it really can help! I've been in counseling for years (which I know doesn't sound reassuring) and it's helped me with a ton of problems, including a less severe version of what you described.
Therapy doesn't mean some creepy old dude asking about your childhood while you lie on a sofa, or not these days. It's someone who is kind, helpful, and nonjudgmental, who honestly wants you to feel better about yourself and your life. It's just talking about your thoughts, feelings, and behaviors and the ways that you can change all three to feel better.
Almost every town or city has a community counseling center that charges for its services on a sliding scale - so if you're broke, sessions are only about five bucks.
If you're worried about telling family that you want counseling (especially if you're under eighteen and need parental permission) just explain that you want to talk to an impartial third party, not someone who knows you and already has opinions, and that the fact that you want help is more important than the fact that you have a problem in the first place.
I wish you luck and hope you can overcome this very harmful problem!

I don't like myself at all. But i trug along everyday.
My psychologist had a name for it.. something like dystormic disorder. I'm just permanently gloomy unless i pull myself out of it. I don't really trust docs much, but she actually made sense.
I truly despise myself. But not enough to stay in bed all day.. I work on improving myself everyday. I just fail each and every time. I guess one good thing is that I'm persistant... At failing. But it could be worse. I could not find the droids I'm looking for.

Only person i dislike sometimes is myself

If I'm my own worst enemy, I don't know it yet.

Yes, every since the day my clone came into existence, he's been doing whatever he can do destroy me.

I'm pretty hard on myself to achieve academically and looking good physically, and I beat myself up over failures. However, that is the very thing that keeps me moving up the ladder, so I guess I'm both my best friend and worst enemy in a way.