Repentance is reviewing one's actions and feeling contrition or regret for past wrongs, which is accompanied by commitment to and actual actions that show and prove a change for the better.
In modern times, it is generally seen as involving a commitment to personal change and the resolve to live a more responsible and humane life. In other words, being sorry for one's misdeeds. It can also involve sorrow over a specific sin or series of sins that an individual feels guilt over, or conviction that they have committed. The practice of repentance plays an important role in the soteriological doctrines of Judaism, Christianity, and Islam. Analogous practices have been found in other world religions as well. In religious contexts, it often involves an act of confession to God or to a spiritual elder (such as a monk or priest). This confession might include an admission of guilt, a promise or intent not to repeat the offense, an attempt to make restitution for the wrong, or in some way reverse the harmful effects of the wrong where possible.
Repentance typically requires an admission of guilt for committing a wrong or for omitting to do the right thing; a promise or resolve not to repeat the offense; an attempt to make restitution for the wrong, or in some way to reverse the harmful effects of the wrong or the omission where possible.
Main article: Repentance in Judaism
Repentance (Hebrew: תשובה, literally, "return", pronounced tshuva or teshuva) is one element of atoning for sin in Judaism. Judaism recognizes that everybody sins on occasion, but that people can stop or minimize those occasions in the future by repenting for past transgressions. Thus, the primary purpose of repentance in Judaism is ethical self transformation.
A Jewish penitent is traditionally known as a baal teshuva (lit., "master of repentance" or "master of return") (Hebrew: בעל תשובה; for a woman: בעלת תשובה, baalat teshuva; plural: בעלי תשובה, baalei teshuva). An alternative modern term is hozer beteshuva (חוזר בתשובה) (lit., "returning in repentance"). "In a place where baalei teshuva stand", according to halakha, "even the full-fledged righteous do not stand."
Main article: Repentance in Christianity
Repentance is a stage in Christian salvation where the believer turns away from sin. As a distinct stage in the ordo salutis its position is disputed, with some theological traditions arguing it occurs prior to faith and the Reformed theological tradition arguing it occurs after faith. In Roman Catholic theology repentance is part of the larger theological concept of penance.
Main article: Repentance in Islam
Tawba is the Islamic concept of repenting to God due to performing any sins and misdeeds. It is a direct matter between a person and God, so there is no intercession. There is no original sin in Islam. It is the act of leaving what God has prohibited and returning to what he has commanded. The word denotes the act of being repentant for one's misdeeds, atoning for those misdeeds, and having a strong determination to forsake those misdeeds (remorse, resolution, and repentance). If someone sins against another person, restitution is required.
The Buddha considered shame over doing wrong (Pali: hiri) and fear of the consequences of wrongdoing (Pali:otappa) as essential safeguards against falling into evil ways and further as extremely useful in the path of purification. Also recommended was the regular practice of self-assessment or wise reflection (Pali: yoniso manasikara) on one's own actions in relation to others and the bigger picture.
In Mahayana Buddhism, one of the most common repentance verses used for reflection is Samantabhadra's Repentance Verse taken from Chapter 40 of the Flower Adornment Sutra:
For all the evil deeds I have done in the past
Created by my body, mouth, and mind,
From beginningless greed, anger, and delusion,
I now know shame and repent of them all. 
Main article: Hawaiian religion
Hoʻoponopono (ho-o-pono-pono) is an ancient Hawaiian practice of reconciliation and forgiveness, combined with (repentance) prayers. Similar forgiveness practices were performed on islands throughout the South Pacific, including Samoa, Tahiti and New Zealand. Traditionally hoʻoponopono is practiced by healing priests or kahuna lapaʻau among family members of a person who is physically ill. Modern versions are performed within the family by a family elder, or by the individual alone.
The modern definition of "to repent," according to the Oxford English Dictionary, is "To review one's actions and feel contrition or regret for something one has done or omitted to do; (esp. in religious contexts) to acknowledge the sinfulness of one's past action or conduct by showing sincere remorse and undertaking to reform in the future."
Arabic tawbah. A major theme of the Quran, mentioned over seventy times and with an entire surah (9) titled for it. Usually described as turning toward God, asking forgiveness, and being forgiven. Islam has no concept of original sin, need for atonement, or ecclesiastical confession. Repentance and forgiveness are a direct matter between the individual and God, requiring no intercession. In cases of sin against another person, restitution is required. In cases of sin against God, repentance, remorse, and resolution to change one's behavior are considered sufficient. Although classical scholars emphasized the individual dimension of repentance, many revivalists and reformists have tied individual actions to larger issues of public morality, ethics, and social reform, arguing for reimplementation of the Islamic penal code as public expiation for sins. Sufis understand repentance as a process of spiritual conversion toward constant awareness of God's presence. Muhammad reputedly requested God's forgiveness several times daily.
In order to communicate the truth of Divine Unity, God has sent messengers or prophets to human beings, whose weakness of nature makes them ever prone to forget or even willfully to reject Divine Unity under the promptings of Satan. According to the Qurʾānic teaching, the being who became Satan (Shayṭān or Iblīs) had previously occupied a high station but fell from divine grace by his act of disobedience in refusing to honour Adam when he, along with other angels, was ordered to do so. Since then his work has been to beguile human beings into error and sin. Satan is, therefore, the contemporary of humanity, and Satan’s own act of disobedience is construed by the Qurʾān as the sin of pride. Satan’s machinations will cease only on the Last Day.
Judging from the accounts of the Qurʾān, the record of humanity’s acceptance of the prophets’ messages has been far from perfect. The whole universe is replete with signs of God. The human soul itself is viewed as a witness of the unity and grace of God. The messengers of God have, throughout history, been calling humanity back to God. Yet not all people have accepted the truth; many of them have rejected it and become disbelievers (kāfir, plural kuffār; literally, “concealing”—i.e., the blessings of God), and, when a person becomes so obdurate, his heart is sealed by God. Nevertheless, it is always possible for a sinner to repent (tawbah) and redeem himself by a genuine conversion to the truth. There is no point of no return, and God is forever merciful and always willing and ready to pardon. Genuine repentance has the effect of removing all sins and restoring a person to the state of sinlessness with which he started his life.