The phrase "fell flat on face" describes a humiliating and embarrassing experience. Instead of using this negative expression, you can use words that have opposite meanings to show positivity and confidence. Some possible antonyms for the phrase include "succeeded with flying colors," "nailed it," "performed flawlessly," "hit the mark," "excelled," "thrived," "achieved greatness," "shined," "earned an A+." By using these antonyms, you can reframe the experience and turn it into a positive one, highlighting your successes and accomplishments instead of focusing on your failures.