How do people get that feeling? I don't remember being carefree ever in my life. I can imagine being carefree but I also can imagine taking a walk on the surface of Mercury. Childhood is such a crappy time filled with school, illness taking forever, boredom taking forever, being tired, hurt and in pain. Each time I finished some school I felt awesome because I knew I won't have to deal with that crap and those teachers anymore. Best thing about school is that when holidays come you can forget all you learned last year. No-one will ever examine you on that. I remember growing up as progressing freedom to not do the stuff I don't want to do. Life was definitely easier as it went.
The joy I remember from childhood was reading books about physics and chemistry and running experiments in my head. I'd be delighted if someone gave me internship in some lab where I could help with actually performing them.