I only really feel like an adult when I spend time with kids and young people. Even though the students I teach are at university, and thus technically adults... I'm always struck by how often they seem 'immature'.

And to be clear, I don't even really mean that as a criticism. Sure, at times they don't pay attention and forget to do things and seem akward/nervous. But "adults' do all those things too. The difference is the adults have generally accepted these flaws and come up with coping strategies (both good and bad) like avoiding those situations, or blaming other people.

So, what makes me feel like an adult is not that I'm on top of things, or that I'm no longer a mess. It's that I know I'm a mess, and I no longer hope that one day I'll get everything sorted, and tbh, that's fine.