I was a research scientist who re-trained as a maths teacher.
What my 1st career gave me was the confidence to pick maths as my specialist teaching subject. Teaching is something I’d considered on and off from childhood, partly because I come from a teaching family: my mother, aunt, and several great-uncles and -aunts were all teachers. When I was at school, I LOVED maths and felt like I was pretty good at it, but somehow my grades didn’t reflect what I felt was my ability. As a result, I became disillusioned, and decided I just wasn’t that good at maths, and wound up doing a psychology degree. During that degree, I performed far better in statistics than I did on most of my psych classes. I did a MSc where I developed mathematical algorithms for locating and identifying vowel phonemes in speech. Then I did a PhD where I mathematically modelled brain function in the early visual cortex. Then I lectured in statistics at MSc and PhD level. Maths, maths, maths: enough to apply to train as a maths teacher, even though my school maths qualification was not great.
It was during this re-training that I was diagnosed as dyslexic for numerals. I mix numbers up, write them down backwards, forget them and/or the operands, etc., etc. On the other hand, I can visualise mathematical concepts like calculus or path analysis in my head. Fortunately, the diagnostic report was very detailed, virtually an instruction manual on how to avoid my specific problems, so I totally aced my teacher training.
It probably also helped that my BSc, PhD and subsequent research/lecturing gave me practice in standing in front of people and delivering seminar papers and lectures, but I’m not scared of public speaking anyway. Mostly, it gave me back my love of mathematics.