Apology letter to boss

Dear Sir, From many years I am working in this office and I know you can give the guaranty about my work and the professional carrier. But freshly one event occurs which stains my good image and your reputation. So because of this I want to pass my sincerest apology to you. I know that because of this event your feelings are hurting. I also want to tell you that it was not planned. With my good intention I m writing this letter. Yet if this is not enough I m going to pay cost for my misbehavior.Also if my attendance in office spoil the image of the company then I m going to resign my post. Sorry again and thank you very much. Yours sincerely, John Brennan