What does "make you feel four inches long in every direction" mean?

[Aronsept]

this is the passage:

I asked her again, 'Why can't you use your own bedroom, that’s what it's there for.She said, I can’t sleep and work in the same room. I need a study.She said it as if a study is one of those things you can't do without, like clean water. I said, 'But I need to exercise.' She said, You’re fourteen. Your body isn’t even developed. The only thing you need to do is stop beating the bishop before you go blind. This was classic Kelly. She always knew how to make you feel four inches long in every direction.

i dont understand the last sentence, who can help me? thank you.

[Mister Micawber]

.
Do you understand 'beating the bishop'? That is a clue.
.
_________________
Native English teacher at Mister Micawber's

[SkiIucK]

:D