תשובה Teshuva, Repentance can actually be done any time, but this is the season when we are all reminded that Gd makes a special accounting of our sins and mitzvot, the Gd given Torah Commandments. By Rosh Hashanah, 5776, which is just over a week, we should be on our way to complete repentance. Ten days later on Yom Kippur, Gd makes His decisions for every single one of us.
Teshuva can also be described as a transformation, because Gd permits and accepts us as a new person, cleansed of sin. We can resume our life transformed into a better person, a better Jew.Maimonides on Repentance"What constitutes complete repentance? He who is confronted by the identical situation wherein he previously sinned and it lies within his power to commit the sin again, but he nevertheless does not succumb because he wishes to repent, and not because he is too fearful or weak [to repeat the sin]. How so? If he had relations with a woman forbidden to him and he is subsequently alone with her, still in the throes of his passion for her, and his virility is unabated, and [they are] in the same place where they previously sinned; if he abstains and does not sin, this is a true penitent" (Mishneh Torah, "Laws of Teshuva," 2:1). (Jewish Virtual Library)