How is everything going? I am writing to beg your pardon for my not being able to join you for the trip to Beijing next weekend which we planned before.
I have been looking forward to the trip for a long time and have done a lot of preparation. However, I am informed that the CCTV national English competition is going to be held on that day. You know that I've been waiting for the chance for months and thus by no means can I miss it. As a result, I cannot make it for the trip. I’m sure if you were me, you would make the same choice. I do hope you can accept my apologies and understand my situation.
Please allow me to say sorry again.