What's "mental block" mean?
Native speaker’s answer
If one has a "mental block," it means they can't think about or do something because something in one's mind prevents them from doing or thinking about it. So here, something in her mind prevents her from riding the subway. Ex: When it comes to my childhood, I get a mental block, and I just can't think about it. Ex: I had to get over a mental block before I could go sky-diving. Ex: She gets a mental block with names. She always remembers faces, but not their names.