I always figured that eventually I would "mature" in terms of social and functional development, but it just never happened; I seem perpetually stuck with a child's mind in an adult body, having made no progress at all since my early 20s.
That literally describes every single adult I know from my generation.
The only adults I don't have this perception of are the ones that are significantly older, and/or I don't know them well. And it's probably mainly due to the latter.
As for me I don't want kids. And that can be an issue if you're in a relationship with someone who does.