you had just missed a friend's party,write a letter to apologise. apologise to your friend explain why you couldn't attend the party tell her what steps you will take to avoid missing it in the future.

Dear Sara, I m writing this letter to you know that the sincere apologise towards i couldn’t attend your birthday party on the last week. i know you are little angry with me, but i was in a troubled situation. First of all i show my sincere apologise regarding that i skipped your birthday party. […]