How disappointing!
真令人失望。
It's disappointing.
我很失望。
I'm rather disappointed.
你讓我失望。
You let me down.
他沒有我想象的那么好。
It wasn't as good as I expected.
真可惜。
What a shame!
很可惜。
That's a real pity.
太糟糕了。
That's too bad.
那只是白費力氣。
That was a waste of effort.
都是我不好。
It's all my fault.
我搞雜了。
I screwed up.
白費我那么多的努力。
All that for nothing.