Teshuvah is medicinal healing:[1]
Repentance is similar to a medicinal act of healing as the verse states, “and I will heal those who return.” Just as medicine for physical healing of an illness of the body is more expensive and more sublime than food of the body through which man is able to live, so too, repentance is on a much higher level than the actual Mitzvah’s as it draws down vitality of the soul from the name of Havayah and is able to fill and heal the soul of all the blemishes and lacking of G-dliness which result from sin, as explained previously.
[1] Likkutei Torah p. 45b