I too think of my own death in various situations quite frequently. Keeps me awake at night. The best way I have found to break my mind out of that loop is to distract myself with something that is complex so it requires more concentration. Puzzles, games, books (depending on the book) talking to people about something in-depth (not the weather). Those are all things that I have found to be helpful but not all the time, sometimes I just have to get too tired to keep thinking anymore.