Everybody miss their childhood days..because those days were being the most enjoyable days of our life.
We used to have fun, play games, run and fall, get beaten and scold.
One can't specify a most enjoyable part of his/her childhood because this stage is itself filled of enjoyable moments.
But did you know as we grow up, as we become mature, as we know the difference between right or wrong, as we know the reasons for something, as we understand everyone's point, as we become enough able to face the ups and downs of life, as we know that this world is nothing..this life is nothing but a journey full of adventures, and at that point we lose our childhood and enter to the adulthood.
But it's not impossible to get into our childhood again. We can get in by enjoying, by taking some time for ourself, by spending some time alone with ourself, by being a child with a kid...we can feel those days.