Gomenasai, I know i let you down.

对不起，我让你失望了。

youdao

And when I let you down, it will not be because I desire to hurt you, nor because I do not still love you.

当我令你情绪低落的时候，不是因为我渴望伤害你，也不是因为我不再爱你。

youdao

If you put your trust in me, I will not let you down.

你要是信赖我，我就不会让你失望。

《牛津词典》

Now, let's imagine I've been very lucky and gotten to you-- just get down on your knee.

现在,假设我非常幸运地伤到你了,请蹲下

耶鲁公开课 - 古希腊历史简介课程节选

I've done my best to be your friend, but I also let you down and I let my family down and I let this country down.

CNN: Transcript: Clinton's remarks at Orlando fund-raiser

"I know many have been so supportive during this campaign and I hope I have not let you down, " he wrote.

BBC: Lee Baron, Labour

"My mother told me not to talk too long today and Barbara, I will not let you down, " Clinton quipped Thursday, prompting laughs from Hillary Clinton.

NPR: The Bush And Clinton Families, On Stage In Texas