You had promised to attend an important event with your friends, but you were unable to be present due to a personal reason. Write a letter of apology to your friend, explaining the reason for your absence and expressing your regret. Don't forget to suggest a way to make amends or fix the situation.

Dear John, It’s with huge regret that I write this letter to present my apologies for missing your birthday party. I’m extremely sorry for having missed your birthday celebration. I know that it was a special night for you and I can’t say how much I’m ashamed to miss this special night and occasion to […]