The Rebbe counters a doctor's discouraging prognosis, citing the Tzemach Tzedek that doctors are given permission only to heal, not to dishearten. He encourages faith in Hashem and practical steps, including diet. He praises the wife’s uplifting Torah talk as proof that spiritual growth brings physical well-being.
https://www.torahrecordings.com/rebbe/igroskodesh/015/010/5499