Antonyms for the phrase "threw into a tizzy" include terms such as calm, composed, and collected. These words denote a sense of control and ease, rather than the feeling of being overwhelmed or flustered. Other antonyms for being thrown into a tizzy may include words like unflappable, cool-headed, or level-headed, which are all adjectives used to describe someone who remains calm and rational in the face of stress. Using these antonyms can help to communicate a different, more positive tone and can help create a sense of reassurance or stability in otherwise chaotic situations.