on second thought

Idioms  

1. Resulting from a revised opinion or change of mind, as in I thought I'd go to the movies, but on second thought I'd rather stay home. Similarly, have second thoughts means “change one's mind,” as in I've had second thoughts about moving to Florida. This idiom alludes to ideas that come later. [Mid-1600s]

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Example Sentences

Then: "On second thought, I changed my mind."

From BBC

“On second thought, an embrace would be unseemly,” she concluded, “but perhaps I could invite him to tea, as a way of saying thank you.”

From Literature

On second thought, maybe they simply aren’t.

From Los Angeles Times

On second thought, maybe I overstated their brilliance.

From The Wall Street Journal

Then: “On second thought, I changed my mind.”

From Los Angeles Times