You Were an Achieving Kid
When you were a kid, people often remarked on how mature you seemed. You acted quite adult.
You excelled at school, and you actually enjoyed it to a large extent. No one had to ask you to do your homework.
As a kid, you were probably a bit picky. You liked structure, schedules, and organization.
You had trouble being friends with regular kids. You probably were only friends with other serious children.
Yeah, I wasn't real organized but I liked school, I made good grades and the grown ups called me "mature."