I'm anxious that we get there on time because I don't think there'll be many seats left.

anxious 是形容词，来自名词 anxiety（焦虑），基本意思是"焦虑的、担心的"。在这个句子中，anxious 表示"急切地希望某事发生"，带有"担心无法实现"的隐含意味。