Antonyms for the phrase "being on guard" can include feeling relaxed, unworried, carefree or unguarded. Being on guard is often associated with vigilance or watchfulness, but the opposite can be characterized by being oblivious or inattentive. In some cases, people may feel confident enough to let their guard down and trust those around them. It is important, however, to remain aware of potential dangers and not become complacent. The opposite of being on guard does not mean being careless, but rather being able to relax and feel secure in a safe environment.