Jawaban:

Dear [Best Friend's Name],

I hope this letter finds you in good health and happiness. I am writing this letter to express my sincere apologies for not being able to attend your birthday party this year. I was looking forward to it and had planned for it in advance, but unfortunately, some unexpected circumstances have arisen, and I won't be able to make it.

I know how much this day means to you, and I feel terrible for letting you down. I wish I could be there to celebrate with you, but I promise to make it up to you in the best way possible. Maybe we can have a one-on-one celebration once things settle down a bit, and I can make it up to you in grand style.

I hope you can understand my situation and know that I am with you in spirit on your special day. I want you to know that you are always in my thoughts, and our friendship means the world to me. I hope you have a fantastic birthday and enjoy every moment of it.

Once again, I am deeply sorry for not being able to attend your party. Please forgive me, and let's catch up soon.

Sincerely,

[Your Name]