The High Holidays provide a special opportunity to repent.
Excerpted with permission from The Jewish Religion: A Companion, published by Oxford University Press.
The usual word for sin, averah, is from the root avar, "to pass over," hence "transgression," overriding God's will, The usual word for repentance is teshuvah, meaning "turning"--that is, from sin to God.
Repentance is acceptable, the Rabbis teach, at any time, but the special time for repentance is the season from Rosh Hashanah to Yom Kippur, the Ten Days of Penitence. In all the rabbinic sources, repentance involves two things: remorse at having sinned and confession of the sin. The numerous rabbinic statements regarding sin and repentance are scattered through the Talmudic literature and are not presented in any systematic form. A useful summary is given by Maimonides (Teshuvah, ch. 1 and 2), although the very attempt at systemization departs, to some extent, from the openness and fluidity of rabbinic thought.
Maimonides on Repentance
Maimonides writes: "If a man transgresses, wittingly or unwittingly, any precept of the Torah, whether a positive precept or a negative, and repents and turns away from his wrongdoing, he is obliged to confess his sins to God, blessed be He. How does a man confess his sins? He says: 'O God! I have sinned, I have committed iniquity, I have transgressed before Thee by doing such-and‑such. Behold now I am sorry for what I have done and am ashamed and I shall never do it again.' What constitutes true repentance? If the sinner has the opportunity of committing once again the sinful act and it is quite possible for him to repeat it and yet he refrains from so doing because he has repented‑-for example, a man cohabited unlawfully with a woman and, after a time found himself alone with her again and he still loves her and is still as healthy as ever and it takes place in the same province in he had previously sinned with her and yet he refrains from repeating the transgression--he is a true penitent....
Repentance on Yom Kippur can only win pardon for offences against God such as eating forbidden food or illegal cohabitation and so forth, but there is no forgiveness for offences against one's neighbor such as assault or injury or theft and so forth until the wrong done is put right. Even after a man has paid the restitution due to the victim he must beg his forgiveness. Even if all he did was to taunt his neighbor [i.e. and the question of restitution does not arise] he must appease him and beg his forgiveness. If the victim does not wish to forgive him he should go to him in the company of three friends and they should beg him to grant his pardon. If their efforts were of no avail he should repeat the procedure with a second and a third group but if the victim still persists in his attitude he should be left alone and the victim is then sinful in refusing his pardon."