Trust is one of the most important factors in a successful long term relationship because most people cannot be with their partners every hour of the day and night. Part of that trust is the knowledge their partner will not become emotionally or sexually active with another person. When a partner cheats, it is often devastating to the relationship. It causes immediate emotional pain, and many relationships cannot be salvaged when this occurs. The person who cheated needs to earn the trust of their partner yet again if they want to continue to be with them.
It is incredibly difficult for many people to trust someone who has already betrayed them once. If a cheating partner asks for a second chance, this is likely the last chance they will ever get to remain in the relationship. Earning their partner's trust again is difficult, and it requires complete openness and honesty at all times. Few receive this gift of a second chance, and those that do have a special partner who should be cherished in the years to come.