On second thought, ... 仔细想了之后，……
1. On second thought, I'm going home on this vacation.
2. I'll do it, on second thought.
3. On second thought, I won't tell her the truth.
A: Would you like a cup of coffee?
B: No, thank you.
A: I'm going to get one for myself. They make really good coffee here.
B: On second thought, I will have a cup.