The mind controls so much of the body. We are much more than flesh and blood we are complex systems. Patients do better when they have faith that they're going to do better. That's why I always tell my patients and their families not to neglect their prayers. There's nobody I don't say that to.
To work without attachment is to work without the expectation of reward or fear of any punishment in this world or the next. Work so done is a means to the end and God is the end.