We generally write an apology letter to make the reader understand the true reasons of committing the mistake which we are not able to convey verbally. It is quite important to explain the reader that under what kind of circumstances the mistake was committed. By writing an apology letter, the reader comes to know that the writer has the guilt of making a mistake. It also insures that the writer will not commit such a mistake again.
878 Septa House
12th May 2010.
I apologize for my recent inability to come to your house for your birthday. I had spoken to your wife about baking a cake for you and make your birthday special. But unfortunately I got stuck in some office work and had to postpone my schedule for 5 days. I was present at Denver on the very day of your birthday was scheduled but got asleep due to heavy travelling schedule. When I woke up, the time for baking the cake had already passed out so I had to go to a bakery shop and get a cake from there.
Brother, I am extremely sorry that I wasn’t able to keep my promise. Broken promises really hurt big. I apologize for my mistake and it won’t be repeated again. Please forgive me brother.
Your beloved brother,