Some evolutionary psychologists theorize that guilt and shame helped maintain beneficial relationships, such as reciprocal altruism. If a person feels guilty when he harms another, or even fails to reciprocate kindness, he is more likely not to harm others or become too selfish. In this way, he reduces the chances of retaliation by members of his tribe, and thereby increases his survival prospects, and those of the tribe or group
Most people when discovered as doing wrong to someone feel guilt, however a few of those people aren't sorry for what they've done they worry about losing the benefits from the person they wronged or worry about retaliation which causes them to seek approval that there are no "hard feelings" and that everything really TRULY is OK.
Guilt and its handmaiden, shame, can paralyze––or catalyze one into action. Appropriate guilt can function as social glue, spurring one to make reparations for wrongs.
As with any other emotion, guilt can be manipulated to control or influence others. As a highly social animal living in large groups that are relatively stable, we need ways to deal with conflicts and events in which we inadvertently or purposefully harm others. If someone causes harm to another, and then feels guilt and demonstrates regret and sorrow, the person harmed is likely to forgive. Thus, guilt makes it possible to forgive, and helps hold the social group together.