Mary seems to demonstrate the quality of "optimism", which has been shown to somehow buffer the effects of stress and illness.
Optimism is a psychological disposition mirroring a conviction or expectation that the result of some particular undertaking, or results by and large, will be sure, ideal, and attractive. Appreciation is related with hopefulness and has been resolved that thankful individuals are more joyful, get more social help, are less focused, and are less discouraged.