The phrase "most chin up" is an idiomatic expression that means to stay optimistic, hopeful, and confident even during tough times. Some antonyms for this phrase could be "downhearted," "defeated," "hopeless," "negative," or "pessimistic." These words signify a sense of giving up or losing faith in oneself or a situation. By contrast, staying "most chin up" means one is determined to remain steadfast and resilient in the face of adversity. It's important to remember that everyone experiences ups and downs in life, and maintaining a positive attitude can make all the difference in overcoming challenges.