To "pull in one's horns" means to become less aggressive or arrogant. Some synonyms for this phrase include "tone down," "moderate," "de-escalate," "humble oneself," "restrain oneself," or "become more modest." These are all ways of suggesting the idea of restraining oneself, becoming more passive, or showing more humility. In particular, "de-escalate" suggests that a situation is becoming less confrontational or dangerous and "moderate" suggests that a person is becoming less extreme or fanatical in their beliefs or behavior. No matter which synonym you use, the idea behind these phrases encourages individuals to tone down their behavior and become more peaceful.
