Stress
Aside from the stress of difficult conditions if you’re performing surgery in third world countries; or the stress of being away from friends and family for a couple of weeks; or the stress of trying to sleep without a mosquito net; or the stress of dealing with other volunteers that you don’t get along with like that one guy who keeps sounding like Annoying Orange; or convincing ornery natives that don’t speak your language and that’s okay; or the stress of trying to go to the bathroom in a hole in the ground – aside from that stuff, there’s really only one main problem:
You can’t fix everyone.
You will want to. You will have dreams of trying to. But you will not be able to do it. Not everyone.
There will always be little children with holes in their faces, or babies that could die from their disfigurement, or teens with charred, melted flesh that you cannot fix because there is not enough time in the world to fix everyone.
You will have to make Sophie’s Choice many times.
You will have to make peace that you are doing good and making a dent to right the wrongs of the world. You are only human.