Most of all, Hugo would do his best to remain invisible. (1.5.56)
After Uncle Claude disappears on him, Hugo has no choice but to remain in the train station and try not to get caught. It’s not a fun life for a kid who should probably be out playing and running (not to mention learning his times tables).
“I can’t…” said Hugo.
“You must,” said Etienne smiling. (1.8.43-44)
Hugo is so trapped in the train station (like a little sewer rat, except nicer and smarter) that he’s hesitant to leave for anything. He has exiled himself within the walls of the train station out of fear for his safety. He doesn’t want to go to the movies with Etienne and Isabelle, but when pressured, he decides to go along with it, showing he just might have an edge on Papa Georges in a bravery competition.
He knew he shouldn’t have gone to the movies. He never should have left the station. (1.9.37)
Hugo is terrified when he comes back and sees the Station Inspector. It’s a serious game of cat and mouse for Hugo, even when the Station Inspector isn’t aware of his existence. He’s constantly on guard about being caught. So even in his home, he's isolated.