When you're a kid, no one tells you what growing up is really like. All we see is that adults had freedom. They could do whatever they wanted and no one told them what to do. They had independence. No one tells you that greater independence requires greater responsibility. Maybe that's what they mean to say with "enjoy being a kid while you can." They forget to mention the whole responsibility thing.
Don't get me wrong. I enjoy my life. But sometimes it would be really nice to have a little less responsibility.
Today I had to fire one of my employees and I felt the responsibility of taking away her employment weigh down on me like a whole offensive line had just dogpiled on me. And I wished for a split second that I could have one day as a kid again.