I see you understand my minds, but making trouble in feelings. Maybe I hurt your heart, or I disappointed you. No matter what it is, I only want to say it to you.

我知道你明白我不是真想和你作对，而是“情绪”在作怪，也许，我伤了你的心，也许，你对我很失望，无论是什么，我只想和你说：对不起。

youdao

I'm disappointed in you—I really thought I could trust you!

你真让我失望—我原以为可以相信你的！

《牛津词典》

I am writing to tell you that we were quite disappointed with your service. We had booked a table, but when we went there at the time as arranged, only to be told there were no seats available.

我想写信告诉你，我们对你的服务非常失望。 我们已经预订了一张桌子，但是当我们按预定的时间去那里的时候，却被告知没有座位了。

youdao

You know, I was not really disappointed, it found something close enough to 3 that I'm happy.

我真的不失望，因为它找到了一个，和3相当接近的数,我还是挺高兴的。

麻省理工公开课 - 计算机科学及编程导论课程节选

You can say to someone near you because you're really sad about it, "I was disappointed."

你心里很难受，你可以对你身边的人说 "I was disappointed."

I was 课堂 - SpeakingMax英语口语达人

If I have disappointed you, I will always be sorry.

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