bajar la guardia

bajar la guardia (first-person singular present bajo la guardia, first-person singular preterite bajé la guardia, past participle bajado la guardia)

1. (idiomatic) to lower one's guard, to let down one's guard, to drop one's guard

• Even when talking about a specific person, you still use the definite article and not a personal pronoun, similar to how one refers to body parts in Spanish (e.g. "lavar las manos").

• “bajar la guardia”, in Diccionario de la lengua española, Vigésima tercera edición, Real Academia Española, 2014