It was supposed to be “impossible” to gain as much muscle as I have in my 40s. The reality is that though it did take a lot of effort, it wasn’t even all that hard.

And no, I do not have good genetics and am not naturally that athletic.

What a lot of people mean by “impossible” is that they don’t want you to even try, as you might exceed them. It’s a de facto proscription aimed to prevent you from getting above your station.