alert, open-eyed, watchful, wakeful, Argus-eyed, wary, regardant, regardful, vigilantelike, warisome, more...

careless, inattentive, negligent, unobservant

watchful, attentive, observant, aware, conscious, cognizant, more...

extra, more, own, french, least, hyper, armed, war, populace, constant, english

on one's guard,   on the lookout,   hyper aware,   on high alert,   always watching,   not complacent,   on the lookout for,   on the look out,   be alert,   being alert