Het up is an informal expression that means being highly agitated or upset. The antonyms for het up include calm, serene, tranquil, peaceful, relaxed, and composed. When someone is calm, they are at ease, and their emotions and thoughts are steady. Serene means being peaceful and untroubled, while tranquil implies a free-of-turmoil mental state. When someone is peaceful, they are not being bothered by stress, anxiety or tension. Relaxed means feeling a sense of comfort, and someone who is composed is collected and composed under pressure. To sum up, using the antonyms for het up shows expressing a sense of inner tranquility and peace.