a weak moment
A moment when one fails to have the discipline to act according to one's principles or better judgment and instead does something regrettable. I admit that, in a weak moment, I accepted a bribe to allow development to proceed without proper safety measures in place. I'm so sorry I cheated on you. It was a weak moment, and I'm ashamed of what I did.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a weak ˈmoment,
a moment of ˈweaknessa time when you do or agree to something you would not normally do: In a weak moment I agreed to let them stay at our house, but later I wished I hadn’t. ♢ I was on a very strict diet but in a moment of weakness I ate a cream cake.
Farlex Partner Idioms Dictionary © Farlex 2017