What should I think about a friend who cancelled something the day before we went because he said he was anxious?

Mum said that's rude and if he cancels now, you can't expect him to ever keep his word again. But I understand being afraid of going outside. Anxiety is horrible and it might not just be because he doesn't want to go. In fact, maybe he wants to go very much.
I will still go, but my parents paid for our tickets.