A friend asked me this last night and my unprepared answer was all over the place, but I think in retrospect there was a theme. I was aware that being a parent changes the brain in the abstract. I was unprepared for the experience for how hard it hits.
Think the stepson being only a few years from being an adult gave me false expectations. He wants to be treated as a responsible adult, so I try to both hold him accountable for his behavior while explaining a big part of being an adult is sacrificing whim and short-term fun for long-term gain.
Being the father of a tiny helpless human is completely different. And her transition into taking agency and navigating how to balance them has me constantly on my toes. It has completely shifted my world view in places. And I am sure that some decisions over the past year have been completely different due to this shift.
So, this past year has been a lesson on how psychology textbooks are not completely full of abstract bullshit.