what does it means?

[kombucha]

tell me please what does this phrase means "let your guard down"
thank you beforehand.

[Mister Micawber]

To 'let one's guard down' is to slacken one's defense, either physically (as in a karate match) or emotionally/intellectually (as when one is overly susceptible to infatuation)-- in either case, one becomes vulnerable to attack.