Remorse, a noun, is what you feel if you regret your actions or wish for another outcome.
The noun remorse has a very vivid origin. It comes from the Latin roots re for "again" and mordere "to bite." So, if you feel remorse, it means that your conscience is working on you, your past actions are biting you back, and making you feel very regretful. Synonyms for this word are "penitence," "rue," and "contrition." If you took a cookie from the cookie jar and ate it you can't return it; all you can feel is remorse for what you did!