The literal meaning of “repentance” (teshuvah) is “return”—the return of the world to God, the return of the divine soul to its source, which is also the source and root of all worlds.
We achieve such atonement when we perform "good deeds" -- when we study Torah and perform the mitzvot.
This comprehensive teshuvah is comprised of Torah study and divine service (in particular, prayer).
A person engages in that worship with great joy, for it represents the soul's liberation from the body, with its sensory perceptions and desires.
It brings about renewal and the emergence into the freedom of divine holiness.
A person who is in a state of repentance throughout his life is not someone who must atone for a particular sin but someone who is returning to God, to the source and root of his soul, coming ever closer and growing ever more intimately connected to Him, walking upon the path that reaches to infinity, a path without end on which one walks forever, "in this state of repentance throughout one's life."
From Understanding the Tanya by Rabbi Adin Steinsaltz, chapter 31, p.106-107