on (your) guard

to be careful and aware because a situation might be dangerous.

I resent this attitude that you can't trust anybody, that you always have to be on your guard.

• the better part of something
• the Bible Belt
• the big daddy
• the bigger they are, the harder they fall.
• the big picture
• the big smoke
• the big time
• the bird has flown.
• the birds and the bees
• the biter bit
• the biter is bit
• the bitter fruits
• the black sheep
• the black sheep of the family
• the blind leading the blind
• the blue blazes
• the boot is on the other foot
• the bottom drops out of the market
• the bottom falls out of the market
• the bottom fell out
• the bottom fell out of
• the bottom fell out of something
• the bottom line
• the bottom of the barrel
• the bottom of the heap