C'sav Yad of Reb Noson of Nemirov z"l in a letter written to one of his closest students, Reb Meir Mirkis of Teplik z"l, Reb Noson z"l writes [partial translation]:
"You know that our only strength is tefilah and I have raised my hands to Hashem to help you from His Holy Place... a complete and speedy recovery from Heaven, a cure for the soul and a cure for the body.
"But, my dear friend, my request of you is that you strive with all your might to gladden your soul. Joy is the remedy for all sicknesses (שמחה היא רפואה לכל התחלואים). Be strong and brave and trust in Hashem Who will not forsake you and all will be transformed to good."