A Fobia
When you're so scared of doing anything fun that you'd rather just sit in the corner and stare at the wall.
I got a phobia. I didn't go to the party. I just sat in the corner and stared at the wall.
My friend has a phobia. He didn't go out. He just sat on the couch and stared at the ceiling.
My dog has a phobia. He didn't go on a walk. He just sat there and stared at the wall.