Wiktionary
vb. (context idiomatic English) To change one's opinion, or be uneasy about a previous decision.
Usage examples of "have second thoughts".
I set a spell upon her to keep her asleep, for I was beginning to have second thoughts over the wisdom of making this journey.
I said, even though the thought of mouthy little children getting into things made me have second thoughts about what I was saying.
Some, apparently, began to have second thoughts about the reckless advanceĀ.
She began to have second thoughts about gifting it to Rika, but she supposed if anyone could handle the beast, it would be Auntie Rika.
Every day they delay is another day in which they can have second thoughts.
Archer began to have second thoughts about his implants after a tabloid reporter for the galactic net asked him if he purposely always placed himself in danger in order to compete for the most dangerous missions.