the more direct the experience, the harder to talk about... why?

i was thinking about "brain freeze", an expression people sometimes use when they can't think of something. i wanted to ask, when people use that expression, what is the actual experience they're describing? is it just applied rhetorically in retrospect if you happen to not be on the ball? or is there some really distinct feeling, like a brain-state movement? i was thinking that it's kind of hard to phrase this question in a way so someone could understand what i'm trying to ask. how do you talk about "brain-state movements"? "now it feels like this...."

and then i was thinking that, paradoxically, the most abstract (distanced from direct experience) things are the easiest to talk about. in the limit, you have formal systems that can be perfectly described with no ambiguity, and no one has ever experienced a formal system. on the other end of the spectrum, looking at a block of wood. it's pretty hard to describe the essence of that experience.