I would like to think that it doesn't happen often, but truth being said, I don't know how often I make this mistake when teaching: assuming that something as natural to me as breathing, is also equally evident to everybody else. It happened when I started teaching UV mapping.
Basically, UV mapping consists in "laying flat" your 3D model, so you can create a texture for it (textures are flat entities). In my mind, that was exactly the same as playing making my own cardboard dolls and items, an activity I devoted myself for a long time while I was a little girl.
My world was a world where my parents had to skip dinner so my brother and I could have it. Their budget was pretty tight, and clearly, toys for the little kids wasn't a priority. But there was cardboard, there were color crayons I used to steal from my aunts in my summer visits, scissors and glue. I spent hours figuring out how to design my own toys, trying to make them "real", "3D". I didn't know what I was doing at the moment: I was mentally seaming and unwrapping 3D models on cardboard. It became natural to me, and I assumed that everybody else had similar experiences with cardboard games. To my surprise, these experiences weren't that common, and some of my students don't even recall to ever have constructed a dice from cardboard, which is one of the basic layouts to use.
That's how I built a whole unit assuming that everybody would naturally knew where to seam basic models. And with that assumption I went into explaining how you would cut and align the pieces of your models, to make understand how hard it is to do it manually, so I could introduce how Blender marks seams and cuts and aligns the pieces for you. And then I went into showing how our UV map can tell us where are structural issues in the geometry. And then I finally explained one way to decide where to place the seams, based in decisions we can take when seaming simple primitives.
And there it was: confusion. I seemed to be almost the only one clearly knowing why we had to seam at all, and visualizing the relationship seams-unwrapped model. Barely nobody knew why I was taking those decisions, how they would apply them on their own... Why I was doing everything I was doing. It actually was a struggle.
So 167 pages after, I decided to sort of start again. Taking advantage of the fact that we already knew the tools, we would seam models, from basic to a little less basic, to adding a bit more of detail. I took the chance to introduce more concepts, more insight to the process and nomenclature, and more methods. It seemed to help fixing my initial mistake of assuming that some of my experiences were a common place to everybody. Fortunately, my students have patience with me, and they know we eventually reach to somewhere.
That mistake makes me think (worry) about being too self-centered, and if perhaps my little world is too little. But how does one go about being more social, to learn about more experiences from others, when you're devoted to your work and said work requires concentration?
I don't know the answer.