The phrase "flew off the handle" denotes an uncontrolled outburst of anger or frustration. Good antonyms for this word may include remaining calm, composed, level-headed, collected or restrained. Keeping emotions in check, practicing meditation, breathing exercises, or simply stepping away from a stressful situation can prevent one from flying off the handle. Instead, expressing emotions in a dignified and rational manner, or approaching problems with a measured approach and thoughtful discussion, are powerful techniques to avoid outbursts or extreme reactions. As a result, this can improve communication, relationships, and overall well-being.