Cautious, like careful, means you're on guard. You should be cautious crossing a busy street, or cautious borrowing your sister's new shoes without asking.
A fusing of caution and ous, the adjective cautiousis the opposite of hasty and rash. It actually comes from the Latin word cautus, which means "careful" or "heedful." Cautious people always take their time, always approach decisions thoughtfully, and never "throw caution to the wind." All that wariness may sound tedious, but as Confucius said, "The cautious seldom err."