心安理得 ------ have the peace of mind

例句：
A: He said you didn't help him when he was in need.
他说他在危急的时候，你没有帮助他。
B: Come on! I did help him. I don't know why he said so, but I have the peace of mind.
得了吧！我的确帮了他。我不知道他为何如此说，但是我心安理得。

同义词：
have an easy conscience