Something that was really hard for me to do was to eliminate the negative influences and people in my life. Changing your life, your relationships and friendships can be hard and a really painful experience. But in the long run, it's more painful to stay put where you are if you know you're surrounded by negativity.
When you become more assertive, stronger, more emotionally stable and more confident it is an unfortunate fact of life that there will be people that will try to drag you back down. I can go along for months perfectly fine and then something will happen that will make me feel like I blinked and was launched back into high school. And the funny thing is, that I will always say "I wish I had the knowledge then that I have now." When these petty things happen though, it gives me the chance to put that MO to the test.
See, the thing is, the problems, drama, issues, people.... it didn't matter then and it doesn't matter now. So what if someone challenges something I say, makes fun of what I do or puts me down for something I think. I'm still going to continue doing what I'm doing. And if people still want to attack me or put me down, then that's their problem. Sounds cliche, I know. But while all your negative influences and people put exhaustive amounts of time and energy into making fun of you or telling you why you'll fail, you can put your time and energy into positive things and making things happen.
Everyone has the ability to choose the people they allow into their lives. Don't waste time on the people and things that don't matter. Have compassion for them, but don't spend time on them (your time can be much better spent!).