The phrase "blow steam" means to release pent-up emotions or frustrations. However, there are plenty of antonyms for this phrase that depict a calm and composed state of being. Some of them include staying cool, keeping one's composure, staying collected, remaining calm, keeping a level head, exercising restraint, and maintaining one's self-control. All of these expressions connote a sense of calmness and rationality, and they are particularly useful in situations where tensions are running high or emotions are difficult to control. Thus, incorporating these antonyms into our vocabulary can help us stay rational and composed under pressure.