wary

Synonyms: alert attentive cagey calculating canny chary circumspect considerate discreet distrustful doubting frugal gingerly guarded handling with kid gloves heedful keeping on one’s toes leery on guard on the lookout on the qui vive provident prudent safe saving sly sparing suspicious thinking twice thrifty unwasteful vigilant walking on eggs watchful watching one’s step watching out wide-awake

Antonyms: careless foolish heedless incautious indiscreet rash reckless