Repentance is the way a person returns to the proper path after he has strayed from it. Both someone who transgressed negative commandments and one who failed to fulfill positive commandments are obligated to repent. The way to correct one’s failure to fulfill positive commandments is to renew one’s devotion to good and proper deeds. The way to correct transgressions is through being more cautious about sin and by distancing oneself from a sinful environment. Repentance can be compared to someone who was not following a proper diet and now needs to eat certain foods or avoid certain foods in order to get back on track.

Repentance is an act of repair:

The reason for repentance is to repair a person so he can serve the Creator, may He be blessed, after having abandoned divine service and sinning. Repentance involves bringing back what was lost, whether because of his foolishness about God and serving Him, or because his desires overcame his reason, ignoring what God obligated him to do, or because of connecting with bad friends who enticed him, sinning because of them, and the like…. The abandonment of service of the Creator can be in one of two ways: deserting what the Creator commanded him to do and ignoring it, or acting in a way counter to the divine will and thereby rebelling against one’s Creator.

The repair must correspond to the damage:

If one abandoned the service of God through avoiding doing what the Creator commanded him to do, the way to repent for what he was deficient in is to strive to undertake proper activity…. But if his sin was doing that which God warned him against doing, the way to repair it is to avoid going back to that entire type of act and to try to do the opposite [of his sin].

Repentance is like correcting a nutritional imbalance:

An analogy for this in the natural world is someone who became sick because of malnutrition, either because of not eating what would have preserved his health or eating that which damaged his health and caused it to deteriorate. If he was sick because of not eating nutritious food, the way to return to proper health is by increasing the amount of foods and medicines that are appropriate for his nature until he returns to equilibrium. Once he returns to his healthy state he can eat as normal. But if his sickness came about because of eating foods that are dangerous [to his health], he will return to health by avoiding those and similar foods, and [by eating those that are] the opposite of its nature. When his body is once again healthy and reaches a state of normality, he can eat foods that are in between the two types of foods [the dangerous and its opposite], midway between the two types. (Rabbeinu Baĥya ibn Pakuda, Ĥovot HaLevavot, Sha’ar HaTeshuva 7:1)

Repentance applies not only to sins, but also to personality traits:

Do not say that there is [a need for] repentance only from active sins, like promiscuity, robbery, and theft. Just as one must repent from these, he must also search through his bad character traits and repent from anger, enmity, jealousy, mockery, and from pursuit of money, honor, food, and the like. He must repent from all of these. These sins are more difficult than those that involve an action, for when a person is steeped in these [bad character traits], it is difficult to detach oneself from them. (Rambam, Mishneh Torah, Hilkhot Teshuva 7:3)

Further reading: For more on anger, see p. 194; A Concise Guide to the Sages, p. 421.

The motivation to repent and change can stem from a number of sources. One person might come to it by himself, another might need criticism or rebuke from others or inspiration from the the Torah or the Prophets, and still others are moved to change after they experience misfortune. Even if someone repents on his deathbed, it is still considered acceptable. Nevertheless, repentance that is self-motivated is of a higher order and brings about greater reward than if the impetus to repent comes from external sources.

Self-motivated repentance:

Repentance is divided into different levels – the higher the level the greater the reward it brings… The foremost level, higher than all others, is what our Sages, of blessed memory, spoke about when they said: Who is a penitent? It is someone who encountered sin but separated from it (see Yoma 86b)…. The second level is someone who is also himself inspired to repent, but is motivated by the masses who speak disparagingly about his evil deeds. The person senses this himself, knows that he has developed a bad reputation, and is therefore motivated to remove his bad trait…. The third level is one who is also self-motivated, but is inspired by the time dedicated to repentance – namely, the Ten Days of Repentance – knowing that his life is being weighed, his actions are written in the book, and he will be judged on all hidden matters, whether good or bad.

One who repents after being rebuked:

The fourth level is one who did not inspire himself to repent but was instead rebuked about his evil deeds. He accepted the rebuke and repented because of it. That is also a good practice and comes from upright character…. The fifth level is when a person reads God’s Torah and the words of the prophets, and understands the prophets’ rebukes and parables, their warnings, and the destiny spoken about in their books. He takes the words of the Torah and prophets more seriously than the words of those who rebuked him. He was afraid and worried when he read about the serious punishments coming to “those who twist their crooked ways” (Psalms 125:5), and he returned to God. This is also a good practice and an upright character trait…. The sixth level is someone who was not himself motivated to repent, and also not by one of the [external motivations] we spoke about, but after constantly sinning saw that others were punished for the same sins he has. He was afraid he would die like the others and be punished for his evil deeds.

One who repents only when he feels there is no other choice:

The seventh level of repentance is someone who does not humble his heart because of any of the above reasons until he encounters misfortune and is terrified – whether he encounters suffering through loss of property or the death [of people close to him], for one may be inspired to repentance from any damage or trouble that comes to him…. The eighth level is when a person is inspired to repent in his old age, when his natural drives and his strength have weakened. Also on this same level is anyone who repents because sin is unavailable or impossible…. The ninth level is someone who was not chastised by any of the above, but when the time comes for him to die, he senses that the cessation of his vain life is soon to come and he is afraid about the afterlife and worried about his sins, and he longs to return to God with all of his heart. His thought [to repent] will not be effective if he plans on returning to his old ways if he is healed of his sickness – for this is not included in repentance, as we have said repeatedly, repentance never works for one who intends to return to sin. But this person firmly decided to totally leave his evil path even if he lives [and is healed] from his sickness. Then, in this state of repentance, he leaves the world. Even though this repentance was done out of most extreme weakness, his repentance is acceptable and he receives atonement for his sins. (Meiri, Ĥibur HaTeshuva, Meshiv Nefesh, 1:2)