Mainly the deadlines and timelines. It has been more than just a couple times that I went in to work on a Friday/Monday thinking it was a normal day and then finding out they need me in another state/country in a couple days. Everything seems to pile up at the same time, July and Aug I was working 60-70 hour weeks to meet a deadline. Combine that with my other responsibilities, including the survivability of folks using our equipment, adds up to a boatload of stress.