Fear and Mismanaged Mind?

I’m curious about fear existing because of a mismanaged mind. Brooke teaches that fear is simply a thought/thoughts that can be managed in order to change that feeling. How can this be applied to a situation where someone else has caused physical harm to you in the past, so you know they are capable of crossing that line, and you are fearful of them doing something more to you? I’ve thought about boundaries coming into play here and applying that principle. However, it’s not always a choice to completely avoid being in this person’s presence. So, what if the fear is coming from the thought of “when this happens again,” not “if it happens again” because you know that’s the pattern?