That's one of the tells.
It has become quite natural now, so I really can't find the difference compared to my learning while practicing PR and learning employing PR.
Some questions, how did you know you were really reading? When did you know how to tie shoe laces, what's the test for that? When you have a job, how to you know when you know your job? What test are there?
Usually when you just do it naturally, that's when you've got it. That's when you start looking at taking it to another level if you want to challenge yourself.
Alex