She feels tired all the time but has difficulty falling asleep. 她一直觉得很累,但入睡困难。
but连接的并列句,but前面一个句子主语为she,系动词feels,tired为表语,all the time为时间状语。but后面一个句子,省略主语she,谓语为has,宾语为difficulty,分词短语falling asleep作定语修饰difficulty,另一种说法是have difficulty (in) doing sth是固定用法。
你长大以后要做什么样的人?