http://www.youtube.com/watch?v=889-MBf31ek
It can be difficult to understand. I like to compare it to explaining why you like your favorite food to someone for whom that food tastes terrible.
I've been wanting to write more extensively on this. I'd like to break open my old psychology textbooks and do some research. It is important to consider why people enjoy things in general. Simply put when certain areas of the brain light up we feel happy. What makes these areas of the brain light up is going to differ from person to person. Things that are enjoyable to most people are considered "normal."
On some levels most people can appreciate looking back fondly at the past. This is called nostalgia. Many people can appreciate that children do not have the stresses of adult life. While it would be irresponsible to abandon our adult responsibilities, it is also unhealthy to dwell on your problems all the time. For instance, people who do not take time off from work to go on vacation will often become less efficient at their job and it hurts their productivity.
It is also important to take time every day to do something that you enjoy and to temporarily let go of your responsibilities and problems. I have heard the word decompress used to describe this. A person might do any number of things to decompress. For someone that has an interest in age regression roleplaying this is just one of many things that we do for fun. The primary difference is that with us when we take a break from our adult responsibilities, we sometimes take that a little more literally than most people.