I've decided not to drink because I'm afraid of who I might become while under the influence.
That's good you recognize that!
I've seen the way alcohol makes me behave. When I drink with friends, I become a totally different person; this isn't the kind of person I want to be.
It's good to know your limits. Recognizing activities that are harmful for you and choosing not to engage in them is a very responsible thing to do.
I just don't like this person I become, everything becomes so twisted.
I commend you for your self awareness. Not everyone has the ability to admit their shortcomings.