Stress
There's not really much stress here relative to other careers. You're usually left alone. You love all of your co-workers (which is mostly just you), and the work, while perhaps tedious at times, is always changing and presenting new challenges to keep you on your toes.
That said, there are a lot of people involved in each production, and when the film is in your hands they're all waiting on you. So you'd better get on the ball, put in some twelve- to fourteen-hour days, and make sure your turn-around time is quicker than a cowboy's quick draw.