I tried to remain calm but it was very difficult.

remain 是动词，意思是"保持、维持"，指持续处于某种状态。 calm 是形容词，意思是"平静的、冷静的"，描述一种不慌乱的情绪状态。 remain calm 表示"保持冷静"，指在紧张或困难情况下控制情绪。