watchful, guarded, chary, circumspect. Careful, cautious, discreet, wary imply a watchful guarding against something. Careful implies guarding against mistakes, by paying strict and close attention to details, and, often, trying to use good judgment: He was careful to distinguish between them.
Cautious implies a fear of some unfavorable situation and investigation before coming to conclusions: cautious about investments.
Discreet implies being prudent in speech and action and being trustworthy as a confidant: discreet in manner, in keeping secrets.
Wary implies a vigilant lookout for a danger suspected or feared: wary of polite strangers. 2.
meticulous, discerning. 2, 3.
thoughtful, concerned, solicitous, attentive, heedful, regardful.