let someone down [let ˈsʌmwʌn daun]

以下由轻松背单词网站提供

使某人失望

I did not want him to think I should let him down.我不要让他觉得我会使他丧气。
You can believe in him because he will never let you down.你可以信任他，因为他不会使你失望。