This can help both of you understand each other better, and you may discover that the situation does warrant an apology from you after all.
In the World Wars, the military would send telegrams to families who lost loved ones, using this phrase.
It tells them that you have done what's needed to salvage your relationship by offering a sincere apology and providing whatever form of restitution you can.
Once again, we sincerely apologize and guarantee this will not happen in the future.
An apology letter is a physical document or email that acknowledges a mistake, expresses regret and asks for the letter recipient's forgiveness or patience.
Tell them how much you regret what you did, you know it was wrong, and you value their feelings.