Stress
Do you find not eating for three days stressful? What about not sleeping? What about possibly being killed at any moment? Or captured and dying slowly with a very thorough manicure? Or (our personal favorite) knowing that if you screw up, a lot of innocent people will die?
If none of that bothers you, then the stress level would be pretty low. For most members of the human species, however, this is a ridiculously high-stress job. Most Operators burn out before their mid-thirties and retire from the military altogether. Those who stick around, though, rapidly rise through the ranks.