An 'upbeat mien' is often used to describe someone who appears joyful and optimistic. Other synonyms for this phrase include a 'cheerful demeanor,' 'positive disposition,' or 'buoyant attitude.' These phrases all represent an individual who radiates positivity and who is enthusiastic about life. Other words that can describe an 'upbeat mien' include 'lighthearted,' 'radiant,' 'animated,' or 'exuberant.' When someone possesses an 'upbeat mien,' they can often brighten up a room with their energy and optimism. Regardless of the word used to describe it, this personality trait is a valuable asset that can help individuals overcome any obstacles and achieve their goals.