The most direct statement comes from Orot HaTeshuvah 1.3, which identifies a distinct category of "natural physical teshuvah" (תשובה טבעית גופנית) directed at transgressions against the laws of nature — and holds that once a person recognizes that his own harmful conduct caused the deterioration of his vitality, he resolves to return to the laws of life and of nature, so that life may return to him in its full freshness.
Ein Aya, Berakhot 1:103 adds that the second essential dimension of teshuvah — beyond recovering lost moral sensibilities — is practical habituation: walking in good paths while engaged with worldly matters and material desires in their proper measure, so that the body itself becomes the arena in which teshuvah is completed.
Ein Aya, Berakhot 5:38 presses this further, arguing that as long as one's bodily forces resist the elevation of the intellect, one has not yet reached true completeness; therefore the goal of ongoing effort must be to transform the body's nature for the good, until the rising strength of the body itself elevates the positive qualities of the soul — a dynamic described there as the very foundation of Shabbat delight.
Ein Aya, Shabbat 2:209 ties these threads together by insisting that once wrongdoing has become entrenched in one's very nature, teshuvah cannot remain in the realm of thought and imagery alone — it requires actual good deeds to reinforce and naturalize it, restoring the soul's nature to life.