You don't keep your word. Why didn't you tell me then? I've been looking forward to it. How can you change your mind at last minute?
你不守信用。为什么那时不告诉我呢?我一直都盼望着它呢。你怎么能在最后时刻改变主意呢?
I've got a problem and as I don't know what to do I thought I'd write to you and ask for your advice.
我有一个问题,因为我不知道该怎么办。我想我最好写信给你,征求你的意见。
So, celebrate your success, and invite your parents to celebrate with you, however hard it may be for them. If you continue to be excited about your future, you may come to educate your parents in the same way.