Antonyms for the phrase "was cautious" can include terms such as "reckless," "careless," "impulsive," "rash," and "adventurous." These antonyms convey a sense of acting without forethought or concern for one's safety or the safety of others. Being the opposite of cautious, they suggest a personality that is bold, confident, and often takes risks. In contrast, someone who is cautious tends to be more thoughtful, measured, and deliberate in their actions. Depending on the situation, being cautious or taking risks can be beneficial or detrimental. Ultimately, it is up to the individual to decide what approach is appropriate for the given circumstances.