Dear Mr. Brown,
Much to my regret,I was unable to keep my engagement to meet you at the park gate. I fear you are displeased at my failing to keep my promise, but I trust you will forgive me. Let me explain. My mother suddenly fell sick early yesterday morning, and I had to send her to hospital.
I shall be gladif you will kindly write and tell me when and where we may meet again. I hope to see you soon.
I am excessively sorry to say/tell you that ①_____ (直接表达自己不能实现先前的愿望或约定).②Now, I am writing you this letter of apology to show my deep regret_______ (表达歉意).③Please accept my sincere apology__________(诚恳希望对方能接受道歉). ④I fear you are displeased at _________(表达出自己的心情，并请求对方原谅).⑤I hope you will understand me and excuse me for__________(过渡句). ⑥Let me explain(开始介绍道歉的原因). ⑦The reason for my delay/absence was that _________(阐述自己当时的处境和情况). ⑧I had no way out because _______ (总结自己道歉的原因).⑨Therefore it’s not in my power to___________(希望下次再次实现愿望). ⑩Naturally, I want to suggest ____________. I shall be gladif you will kindly write and tell me when and where you____________(约定下次约会的时间和地点)
We may meet again and I hope to see you soon.