You're right. I had something I really wanted to say, which would have fit into
the conversation if you had said something somewhat similar but actually quite
different from what you actually said, but I overlooked the difference so that
I could say what I really wanted to say.
In other words, I sacrificed the
quality of the conversation (namely, I introduced not only a tangent, but also a tangent rooted in a
confusion) so that I could express some thought that had risen to salience in my solitary mind. My doing that made the conversation worse, and the conversation is what matters, not whether I got to express myself in a way that is quick and easy for me.