Stress
Roofing is hard work, and how your day will go depends almost entirely on the behavior of Mother Nature. An unexpected storm that keeps you from working for three or four days can really throw a monkey wrench into your schedule.
When things that are out of your control are ruining your work schedule, your stress level will probably ratchet up a few points. The best way to manage that sort of stress is to have a flexible attitude—a quality that'll also come in handy when you're dealing with finicky clients, annoying coworkers (yes, even roofers have those), and a lack or excess of jobs. Whether you have too little or too much to do, the stress can still creep in.
The good news is, roofing is physical work and all that exercise is a great stress slayer. Carrying bundles of shingles, tools, and roofing paper up and down a ladder isn't easy, but getting a big job done can be immensely satisfying.