on second thought
US /ɑːn ˈsek.ənd θɑːt/
UK /ɑːn ˈsek.ənd θɑːt/

1.
다시 생각해보니, 곰곰이 생각해보니
used to say that you have changed your mind or that you have a new idea that is better than your previous one
:
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I'll have the chicken, no, on second thought, I'll have the fish.
닭고기로 할게요, 아니, 다시 생각해보니 생선으로 할게요.
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Let's go to the park. Actually, on second thought, it might rain.
공원에 가자. 아니, 다시 생각해보니 비가 올 수도 있겠다.