I am excessively sorry to say / tell you that 直接说出道歉事由 . Now, I am writing this letter of apology to show my deep regret.
The reason for my delay/absence was that 过失的原因 . I had no way out because 自己当时的处境和情况. I hope you will understand me and excuse me for 请求对方原谅的事由. It is my carelessness that results in this situation, so I have to try my best to make up for my mistakes. Naturally, I want to suggest that we should make another appointment(建议下次再实现愿望). I shall be obliged if you will kindly tell me when and where you have convenience.
I am looking forward to your reply at your earliest convenience.
I am now writing these few lines to express my sincere thanks for 感谢事由.
I’d like you to know how much your help/hospitality meant to me. You have a positive genius for 对收信人某一方面的赞美. I not only enjoyed____ , but also_______ . It is just your generous help that makes it possible for me to overcome those difficulties. It is so kind of you to help me through those hard times, which would be cherished in my heart forever.
I hope to have the opportunity of reciprocating. I will feel very honored and pleased if you 表达自己回报的心愿 . I am looking forward to seeing you next time!