I'm my own worse enemy.
Why do you think you're your own worse enemy?
I seem to make poor decisions that affect my life in negative ways.
It is good that you don't want to be your own worse enemy, you should try not to do anything that will sabotage your life. Think about your decisions before you make them and understand how they could affect you in a negative way.
It's too hard to think about all of these things, so I usually don't.
I know it's difficult to make changes but you know that you've made poor decisions in the past and that you have to change this pattern. Make an effort to think about your choices before making them and decide if it's the best decision for your life.