Manz -
I have a list of things I like about me and things I don't like about me. Everytime I start to feel this way I take a look at my list and see what I can do to change one thing I don't like, even just the smallest change.
And after I take a look at all the things I like and decide on what change I'm going to make I actually start feeling much better about myself.
Not that this would work for everyone but thought I'd share how I deal with myself when I start being mean to me.