Kol Nidre, the prayer we say on Yom Kippur eve pleading for release from vows, is very famous. Hatarat nedarim, the halachically effective process for annulling such vows, which many Jews perform just before Rosh Hashanah, is much less so.
Here is how it is done. You stand before three adult Jewish men, who together constitute a beit din, a Jewish court, and read the text of hatarat nedarim that is found in most machzorim, asking for annulment of any vows you have made. (But only vows that concern no one but you and God, such as commitments to take on extra religious obligations. Vows that concern other people can only be voided with their consent.)
The beit din answers, according to the prescribed text, that the vows are null. The process only works if you understand the text. If the Hebrew is obscure to you, then better say it in English.
A commitment assumed through a vow has the force of Torah law. When we make a reckoning of our deeds before Rosh Hashanah, we may wish to extract ourselves from promises to ourselves and to God that we have made, however sincerely, yet broken.