You can think of growth mindset as a deidentification, basically identical to that example of Anna the student except done by Anna about herself rather than by her teacher. “Yet” is a wedge that gets you to separate your concept of you-so-far from your concept of future you. “I’m bad at X” sneaks in an equivocation to imply “now and always.”
Ah, good example!
For me, this illustrates how obviously useful and defensible a fusion can seem—“I am bad at math” can seem like just an empirical fact, and generalization from the past to the future seems like a very defensible heuristic. Nonetheless, using “Yet!” to drive a wedge as you describe turns out to be quite useful.