Stress
Endoscopy technicians tend to be pretty satisfied with their careers (source), which is probably because they know they're helping people. That said, all the warm-fuzzies in the world don't cancel out the high stress level that this job brings. Aside from being on your feet all day with barely half a second to breathe, you'll be working in a place where life-or-death situations are routine. When a sick patient stops breathing mid-procedure, you'll have to have your wits about you.
Then there's the stress of finding something bad in the endoscopy when you were hoping to find nothing. While it's usually the doctor who delivers the bad news to the patient, you'll still know that somebody's really sick—and that there might not be a cure. Knowledge is power, but it can also be a heavy burden. Ask the senior techs for some advice about how to distance yourself from your work.