Perhaps as a way to counter many of the complaints about the series' difficulty, one of the central gameplay changes is a new health system that will automatically heal players to a certain extent. We don't know exactly how this system will work, but it seems to be similar to Halo 1's setup where a certain portion of your life will recharge if you can stay out of trouble for a few moments, but another portion of your life (your "armor," to continue the Halo comparison) will remain missing until you make it to the next save point.