道歉信写作常用句型：
1) I am awfully/terribly sorry for what I have done.
2) I feel very guilty for what I have done to you.
3) I am afraid what I have done has caused many inconveniences to you.
4) I regret to inform. you that I am unable to do…
5) Please accept my most cordial and humblest apologies for…once more.
6) I will try my utmost not to make such a stupid mistake again.
7) I am so sorry to have put you to so much trouble