The speaker spent years avoiding math after a bad teacher, then deliberately unlearned that identity by practicing mental calculation without calculators. They went from calculator-dependent to doing math publicly, showing that any skill responds to intentional practice and dropping the "I am bad at this" story.
I think people give themselves these "I am" statements like, "I'm not this way. I'm the type of person who," and then they box themselves in by immediately no longer trying things because they say, "I'm not that type of person." Until I was in my early 20s, I had an "I am" statement that I am bad at math, and it was because at that point I realized that I was like, I've just been saying this my whole life because in 8th grade I had a bad teacher, or I was a bad student, whatever, but I didn't learn as much as I should have in 8th grade, and so after that point, I basically learned everything until Algebra 2. And then as soon as we got into precalculus, I had a pretty, you know, bad experience. And so then from then on, I pretty much just cheated. In my early 20s, I was like, I need to not make this a thing. And so I decided to stop using a calculator for everything. And so whenever I could do math, I just tried to do it in my head. And I would check with a calculator afterwards and I would see how far off I was until eventually I started getting pretty good at it. Then I started just doing math in front of people because that's what I was doing for the last few years. And people were like, dude, you're so good at math. And I remember the first time someone said that to me, I was like, huh? And so I say that because like everything is— like if it is a skill, you can learn it.
