have second thoughts
Intermediate (B1)neutral
To start doubting a decision you already made.
"He started having second thoughts about moving abroad."
Hear it in context

President Obama recounts the raid that killed Bin Laden | 60 Minutes Full Episodes
60 Minutes · 34:41
have second thoughts and say maybe it makes more

This rom-com has the plot of a horror movie
Drew Gooden · 21:02
But now, like, he is starting to have second thoughts.

Mini Camps Underway and NFL Analyst Bucky Brooks | Lots to Say
NFL · 51:13
And I was starting to have second thoughts because I knew