Pick a character from a story you’re working on, planning, or have finished. (If you aren’t working on one, pick one from a TV show, movie, or book that you like.) Working quickly, make a list of all the best things you can imagine happening in that person’s life. Now, go back and list all the things that have happened, are happening, or could happen to get in the way of those best case scenarios.
This is a good exercise for learning to spot potential sources of conflict and opposition for a plot. In order for there to be tension in a plot, something has to stand between the main character and what he or she most wants.
If you want a journaling exercise instead, or you write non-fiction or memoir, do this using yourself as the “character”. What are the best things that could happen in your life? What is getting in the way of those happening? (Or has gotten in the way, or could get in the way?) What are the sources of conflict in your life? What’s getting in the way of your happiness?