Managing Negative Thoughts

Hi Brooke,
I have been able to notice that I think a lot of negative thoughts. I am always perceived as the happy positive person people like to be around, because that is what I have created on purpose, but when I really listen to my thoughts there is a lot of negativity in my head. An example is all of a sudden, I realize I am thinking of (making up in my head) some situation that may or may not happen in the future where in my mind I am going to have a fight with someone. I do not want to spend my brain time on make-believe. So now that I am recognizing it, to manage my mind, is the recognition and dismissal of the thought enough to start creating a new habit of minimizing this or should I be trying to really understand what is driving these negative thoughts it to try change it? These thoughts do not serve me at all and actually cause anger and anxiety that is not useful.
Thanks so much!!!