What Is This Poem About?

Well, it IS about a guy bumping into a door with his head. But it's also about what happens to his brain after he hits his head. He has his "native simile jarred" and he can't compare things to each other any more; he can't imagine any similes any more.

Usually you think of the effects of a bad head-bump as having your vision or your balance messed up; Frost here is suggesting that the inability to do "literary" things, such as comparing things in similes, is just as dangerous to human beings as the inability to see clearly or to balance themselves physically. That is, our mental, "literary" nature is as important as our physical bodies.

I'm not certain about this but I think it could be about loosing one's faith as they become aware of new ideas. I think the "lace/ My fingers and close my arms in an arc." is talking about how one clasps their hands together in prayer. The "going from room to room in the dark part" is about a child trying to make sense of the world by "going from room to room" and the darkness represents their ignorance about the world. Then a new believe (the slim door) comes to them and they begin to question everything (because their native simile is jarred) and they find out certain things aren't true and "people and things don't pair any more/ With what they used to pair with before."

its about a person whos life catches him off gaurd