don't bring a gun to a knife fight

To bring a knife to a gun fight; to be inadequately prepared for something.
Likewise, bringing a gun to a knife fight,
To overreact and overthink Petty situations

You don't bring a gun to a knife fight as it isn't a serious matter. it isn't a matter of your life and death or your money and legacy.
He brought a knife to a gun fight that day when he was watching everyone else's presentations

by InformationLibrary December 2, 2017