Childhood is a period that all human beings passed with and this period has some special characteristics that no other period has. A lot of people precisely love this period because people still trying to overcome acute nostalgia for their days of childhood. In my opinion I agree that the childhood is the happiest time of a person's life.
As for the first reason which is responsibility. Responsibility is from the most important characteristics that an adult person should have because responsibility is the way to deal with everything at anytime in special and specific ways without disturbing anyone's life. For example, we can see responsibility in everything like work, business, sports, arts, education and the way you spend your money. First, during the childhood no one can ask you about the way you spend your money because you are not responsible for kids or family. In addition to that, no boss to ask you weekly for the report of your work and what is the quality of your work and how much time you worked weekly. However, there are limited responsibility for children like the school education and this type of responsibility is mixed with fun and joy because during the school you can have break or breakfast time with your friends. Therefore, you can play, enjoy and watch TV without any type of responsibility.
Concerning the second reason which is friends. Friends is from the best memories of the childhood for a lot of people because during the childhood you may have a lot of friends that you can play with them, travel with them and study with them. For example ten years ago my friends and I gathered and decided to travel to Hawaii to swim, dive and play soccer. We were playing and enjoying our time together. Also, friends cooperate together in studying and making projects and this makes everything easy as we work and produce new things during our meeting
To sum up, I agree that childhood is the best period in everyone's life because this period lacks responsibility and is full of wonderful friends. Finally, I wish that my childhood is back again to sit with my friends and to be away of responsibility.