Some apologies are not evidence of changed character. This is why when someone cheats in a relationship, gets caught, cries and is forgiven, they may still cheat again.
Sometimes, the only lesson they learnt was how they got caught, so next time they simply become better at hiding it.
This is also why you should never measure remorse only by tears, long messages, gifts, promises or how desperately someone wants you back. If they are really remorseful, it will produce changed behaviour.
An apology acknowledges what happened, accountability accepts responsibility for it but transformation is demonstrated by what a person consistently chooses to do differently afterwards.
Don't listen only to the apology. Watch the pattern that follows it. Think before you forgive a cheat.