Repentance out of love of Hashem is coming from the depths of the heart, with great love and fervor, and from a soul passionately desiring to cleave to the blessed Hashem, and thirsting for Hashem like a parched and barren soil thirsts desperately for water.
For inasmuch as until he repented his soul had been in a barren wilderness and in the shadow of death, and had been far removed from the light of the Divine Countenance, in the greatest possible measure, therefore, now that he “repents out of love” his soul thirsts for Hashem even more intensely than the souls of the righteous who have never sinned.
As our Sages say: “Where penitents stand not even the perfectly righteous can stand”. For, as explained earlier, the tzaddik lacks the penitent’s intense yearning for Hashem.
Only concerning repentance out of such great love has it been said that the penitent’s premeditated sins become, for him, like virtues, since through the sins which previously had distanced him from Hashem he attained when he repented this great love. Thus, his sins affected him in the same way as mitzvot: they brought about within him a greater love of Hashem.
(Tanya Chapter 7)