Dear {Recipient},

Please accept my apologies for joking around at {event}. You were right. That was definitely not the time and place to be cracking jokes. I'm sorry I acted like a fool.

Rest assured I have learned my lesson and you can expect me to display proper behavior in future such events. I promise to not {disappoint/embarrass} you again.

Sincerely,

{Your Name}

Dear [Name],

I am writing this letter to apologize for my recent behavior. I know that I have been sarcastic and unkind in my words and I want to make it right.

I understand that my sarcasm was hurtful and I regret that I have caused you pain. I never meant to be unkind and I understand that my words can have a lasting impact. I want to take this opportunity to apologize for my words and my behavior.

I know that I can be a bit of a smart aleck and that I can be too quick to make a joke. I want to assure you that I never intended to be mean or hurtful. I know that I need to be more mindful of my words and the impact they can have.

I am sorry for the pain that I have caused you. I know that I cannot take back my words, but I want to make amends. I am willing to do whatever it takes to make things right and to repair our relationship.

I hope that you can forgive me for my words and that we can move forward. I value our relationship and I want to make sure that I am not causing any more hurt or pain.

Sincerely,
[Your Name]