Antonyms of foolhardy :
timid, unadventurous, unambitious, fainthearted, fearful, mousy, scary, shy, skittish, timorous, calm, cool, levelheaded, sensible, alert, intelligent, quick-witted, sharp, chicken, chickenhearted, cowardly, craven, dastardly, lily-livered, pusillanimous, recreant, spineless, unheroic, yellow, careful, cautious, circumspect, guarded, heedful, prudent, safe, wary, overcareful, overcautious, responsible.
Examples of usage:
I mention this to show what foolhardy things he was capable of doing, never thinking of the consequences. "Wanderings Among South Sea Savages And in Borneo and the Philippines", H. Wilfrid Walker.
" You are very foolhardy," James said. "Love and Lucy", Maurice Henry Hewlett.
Placed as it was the hut overlooked the trail leading to it from the plain, and should it be defended by determined men, assault by that path would be foolhardy. "Hopalong Cassidy", Clarence E. Mulford.