1. What a pity / shame!
太可惜了！

2. I expected it to be much better.
我原本指望会比这个结果好。

3. What a bummer!
真糟糕！

4. What a let-down!
真让人失望！

5. All my effort went down the drain.
我所有的努力都白费了。

6. I was so looking forward to..
我原来还一直盼望……

7. I messed up.
我搞砸了。

8. That's (just) so disappointing!
真让人失望！