If a person is constantly reliving the past, rummaging over poor decisions or errors they committed and at the same time experience feelings of loss, sadness or disappointment I would suggest the following:
Regret is often expressed by the term "sorry." Regret is often a
feeling of sadness, shame, embarrassment, depression, annoyance, or
guilt, after one acts in a manner and later wishes not to have done
Remorse is an emotional expression of personal regret felt by a person
after they have committed an act which they deem to be shameful,
hurtful, or violent.