This is proving quite hard to articulate as I try to find a way to visualize it.

To me...

Thoughts are like threads to follow and your wall is faceted shell. Each of these facets carries a kind of gravity which pulls on your thread.

Facets you have accepted without understanding appear solid, a barrier. When you run into one you have hit the wall.

Facets where you have no concept are wide open and you're free to follow your thread, but you risk finding yourself adrift with no reference asking for your thread to become tangled.

Facets where you have greater understanding are revealed to be a lattice, full of gaps to thread through and continue exploring.

You don't "leave" the shell, there's always another layer that might be completely new or something you've passed through many times before.

Imagination/discovery is the act of continually finding the gaps.

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Personally, I've always done a lot of visualizing. As an adult I've come to recognize close similarities to what I do in the visualization techniques of Stoicism and general thought experiments.

One exercise I find quite useful is to avoid resorting to references for things I don't understand, to turn first toward visualizing how to create whatever it is that's puzzling me - to "search for the gaps" and see where I end up.