Dear {Recipient},

I'm sorry you were left out of the {activity/event} last {day of the week}. I had meant to invite you but things got really hectic and I lost track of a lot of details… I'm really sorry. This incident has made me realize that I need to ask for help and be more organized the next time I'm planning {a/an} {activity/event}.

I know what it's like to be left out, so I completely understand why you're upset. I'd like to make it up to you by buying you {a coffee/lunch} sometime this week. When are you available? Please let me know.

Sincerely,

{Your Name}

Dear [Name],

I am writing to apologize for my exclusion of you from a recent event. I understand that this was a difficult situation for you and I regret that I did not handle it better.

I want to explain why I made the decision that I did. I was trying to make sure that the event was successful and that everyone had a good time. I was worried that including you would cause tension and disrupt the event. I was wrong to make this decision without consulting you and I apologize for not giving you the opportunity to explain your side of the story.

I understand that you were hurt by my exclusion of you and I am sorry for that. I should have been more considerate and taken your feelings into account. I hope you can forgive me for my mistake.

I want to make it up to you. I would like to invite you to a special event that I am hosting in the near future. I promise that you will be included and that I will make sure you have a great time. I hope that this will make up for my previous mistake and that we can move forward from this.

Once again, I apologize for my exclusion of you from the event. I hope that you can accept my apology and that we can move forward from this.

Sincerely,

[Your Name]

Dear [Name],

I am writing to apologize for my behavior towards you recently. I realize that I have been isolating you and that this has been hurtful to you. I understand that this must have been difficult for you and I am sorry for causing you any pain.

I want you to know that I never meant to make you feel excluded or alone. I was just trying to figure out how to navigate a difficult situation and I handled it poorly. I understand that my actions have been hurtful and I take full responsibility for them.

I can only imagine how difficult it must have been for you to feel like you were being left out. I am sorry for not being more thoughtful about how my actions would affect you. I should have taken the time to think about how you were feeling instead of just focusing on my own feelings.

I want you to know that I value your friendship and I am sorry for not showing it recently. I want to make it up to you and I am willing to do whatever it takes to make it right. I know that I cannot undo the hurt that I have caused, but I hope that you can find it in your heart to forgive me.

Again, I am sorry for my actions and I hope that you can find it in your heart to forgive me. I value our friendship and I hope that we can move forward together.

Sincerely,
[Your Name]

Dear [Name],

I am writing to apologize for my omission. I understand that my mistake has caused you frustration and inconvenience, and I am truly sorry for that.

I let you down by not [describe the action you failed to do], and I take full responsibility for that. I should have been more attentive and responsible, and I regret not fulfilling my obligation.

I understand that my omission has caused you [describe the consequences], and I am deeply sorry for the trouble I have caused. I am truly sorry for not being able to meet your expectations and I will make sure that such a mistake never happens again.

I know that apologies cannot undo the damage caused, but I want to assure you that I will do my best to make it up to you. I am willing to do whatever it takes to make sure that you are satisfied with my work.

Once again, I apologize for my omission and I hope that you can find it in your heart to forgive me.

Sincerely,
[Your Name]