Bajar la guardia

[ROBINDESBOIS]

To drop the guard maybe???

[Perikles]

To drop the guard maybe???To lower one's guard; to let up, slacken one's efforts.

[Awaken]

To lower one's guard; :good: to let up, slacken one's efforts.

To lower one's guard seems best.

[Perikles]

To lower one's guard seems best.Yes, it's a metaphor from boxing.

[Torres]

"Bajar la guardia"
It's got nothing to do with boxing, in many countries of Latin America it means to let someone in your heart once they have hurt you, it is also used to say to keep up your attention.
"No baje la guardia" Don't lose your attention on something

[aleCcowaN]

"Bajar la guardia"
It's got nothing to do with boxing, in many countries of Latin America...
Como dijo Perikles, es un uso figurado que proviene del boxeo, tanto en inglés como en castellano. Por lo tanto tiene todo que ver con el boxeo.