always be on (one's) guard(redirected from always be on my guard)
always be on (one's) guard
Always be especially careful or vigilant; always be prepared for danger or surprises. He's got a lot of tricky moves, so you should always be on your guard! She needs to always be on her guard on those trails—they can be really treacherous to climb.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.