I started to sew when I was about 6, because I copied my mum. I loved doing it, but nothing seemed to fit right and I never really liked anything I (or she) made.
When I was a lot older, I tried again, and I thought 'there has got to be more to this!' I read the pattern and saw that the seam allowance was 5/8 of an inch and thought well that makes sense, an actual measurement, not just what I feel like! I taught myself from the patterns and books, then at the ripe old age of 25, I returned home and taught my mum how to sew.
She had never had any training or read a book of any sort abut sewing, and she was totally amazed when I told her to do such things as iron the pattern before cutting, and having a uniform seam allowance. The first garment she made, we spent a few hours on it, then my dad poked his head in asking to see it. My mum told him it wasn't ready yet, and when he asked what was taking so long, my mum told him "because she is teaching me how to make a blouse, not a floor cloth" as all of her other endeavors had ended up as rags.
My mum now makes (and wears) most of her own clothes, even more than I do, and will tell that story to anyone who will listen!