work (yourself) up to something
phrasal verb with work verb uk/wɜːk/ us/wɝːk/
逐步为（困难的事）做准备
to gradually prepare yourself for something difficult
He's very shy, but he's slowly working (his way/himself) up to letting her know what he feels about her. 他非常害羞，但他在逐渐使她明白自己对她的感情。