Yes, I have worked in health care, in one form or another, for most of my adult life and i have seen patients that should be dead, but make it riding the wave of sheer will. I know it sound cliche, but attitude really does play a part in recovery, and conversely, the opposite is true, people with no will to live, usually don't. I have seen several patient who hang on until a family member arrives, in a few cases, they held on even after we removed life support. I have seen many things that simply defy explanation save for "mind over matter". However, I do not think all ailments can be cured with the power of the mind, there are rare, extraordinary examples in medicine of spontaneous remission of cancer or chronic disease, but i would still bet on the thousands of years of medical knowledge. Just my humble opinion.