The antonyms for "flew off handle" include phrases like "stayed composed", "kept calm", "remained level-headed", "maintained self-control", "stayed collected", and "kept cool". These phrases describe an individual's ability to manage their emotions and reactions in a controlled and rational manner, despite challenging situations. When someone stays composed, they are able to avoid outbursts or impulsive behavior that might harm themselves or others. It's important to practice emotional intelligence and cultivate self-awareness to keep emotions in check, especially in high-stress scenarios. By remaining level-headed, individuals can communicate more effectively, make better decisions, and avoid regrettable actions.