Stress
Doesn't have to be if you don't want it to be. A lot of the stress of being a missionary depends on the sort of expectations you set for yourself. Are you there to change an entire community's way of life? Or are you there to learn and to experience life in another country, doing God's work where, when, and however little you can? Tough, stressful questions, we know.
But there are more daily stresses in a missionary's life. Like, for instance, not having consistent running water. Or trying to mediate some interfaith dispute that's threatening to embroil the entire region. Or simply trying to say things like, "Where can I buy dish soap?" in another language.