let guard down

let (one's) guard down

To become less guarded or vigilant; to stop being cautious about potential trouble or danger. Also worded as "let down (one's) guard." We'll wait long enough for them to let their guard down before we launch our invasion. There will always be people in this business looking to exploit you, so you can never let your guard down.
See also: down, guard, let

let one's guard down

Fig. to stop guarding oneself against trouble; to relax one's vigilance. He never lets his guard down because he trusts no one.
See also: down, guard, let
References in periodicals archive ?
Real results are close, closer than you judge them to be TO FIND OUT MORE CALL 09050 700 438 CALLS COST 75P/MIN ROI: 1560 911 362 [euro]1.25/MIN LET GUARD DOWN
He and Williams will kick themselves let guard down at death.
In the light welterweight category, Brazilian Myke was defensive from the beginning and attacked Kumar who let guard down. Taking advantage of this, Myke scored two points in the first round even as he saved the punches thrown by the Indian.