Second thoughts从字面理解是再想想，而它的实际含义也很相近：
A reconsideration of a decision or opinion previously made.
重新考虑已经做出的决定或意见
一起看看例句：
[新福尔摩斯 S03E02]
Our Mayfly Man was trying to escape the suffocating chains of domesticity and instead of endless nights in watching the telly or going to barbecues with the awful, dreadful, boring people he couldn't stand, he used his wits, cleverness and powers of disguise to play the field. He was... On second thoughts, I probably should have told you about the elephant in the room.
这位露水情人只不过是想摆脱令人窒息的家庭生活，他不想把漫漫长夜浪费在电视前，也不想和无聊乏味难以忍受的人一起去烧烤，于是他用他的机智和伪装来游戏情场。他我转念一想，真该跟你们说屋子里大象的事儿。
[女王 S01E05]
I can make your family's life very difficult should you have second thoughts.
如果你有二心，我不会让你的家人好过的。
[纸牌屋 S02E01]
The passenger door was open, and he was halfway out. They think that... he might have had second thoughts.
副驾座的车门开着，他半边身子躺在外面。警方认为，他可能中途后悔了。
小节：Second thoughts，惯用复数形式。通常表示后悔了，有了与之前不同的想法，做出了与之前不同的决定。
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