There are a couple of tools that can be used to narrow down your topic. Perhaps therapy, meditation or anger management would be helpful.
Mind mapping is another alternative.
This is a creative approach to narrowing down your topic. Simply start with one word and circle it. From the main circle, start writing down any word that comes to your mind and link it from the first. Continue doing this with each word and eventually you will be able to narrow down the subject. Here is an example of what a mind map looks like.