That Montauk book to Law School had some advice on this. Basically, they said to make sure it's a real obstacle, not to reach so you have something to talk about. Also, it seems to me like th emost effective essays are those that take a significant event, describe it well (good writing) and then tie that into law school. This is a little more interesting than the chronological telling of events type essay. So, maybe you could just describe a pivotal moment and then go into how that changed you.
Hope this helps.