Peace of mind is all about happiness. Usually we start searching for peace of mind when 50-60% of our life is completed, but I feel one has to understand the meaning of happiness at a very early age to gain peace of mind. First, every person needs to focus on reducing the unnecessary needs in their life and try to be happy with whatever one has. Parents are the key players in this effort to make children understand how to be happy rather than helping them in getting unnecessary needs. Based on my experience I have seen such parents where they have very little money but still in order to fulfill the unnecessary needs of children they take out loans to make their children happy. The more wants that are fulfilled, the more the expectation of children. Further failing to fulfilling the needs of these children leads to frustration, and they start losing happiness as happiness does not live in all those needs. One person losing happiness impacts multiple people, maybe parents, family, friends, relatives..etc. By now you understand where the basic foundation of happiness starts from. The approach of happiness is applicable to all kinds people, whether they belong to low, middle or upper class.You may be wondering why I have been explaining about happiness to start understanding at a young age and the reason is as the age of a person increases the capability of a person to understand the meaning of happiness is not that easy. You usually might have noticed people start joining yoga, meditation, and gym classes after they get married or when they start working. People at middle age who try to attain peace of mind by doing yoga and meditation gives them temporary peace of mind as it has not been developed within themselves at early age as it is hard to digest peace of mind later consistently.
The above is a glimpse of what and how we loose peace of mind and why.
Now let me explain how one can gain happiness and peace at a very early age with less effort. Make children adopt more natural things rather than artificial things, as natural things are free of cost and long lasting. Examples would be, going to temple, gardening, reading the library, taking them with you for a morning walk, so that they can feel the fresh natural air rather than artificial things built at home. If they wish to have ice cream or any other outside stuff, see if possible that can be home made or bring them home and enjoy it in the home with the family which will give them more happiness and help them stay connected. Spend money on games, clothes, shows, movies but try to keep them within limits. Travel once every 3 months for a short time to different places. I know its easy to say but hard to comply, but if at least 60% of such things are done then yoga and meditation is attained within themselves till long age. Even at any point of time if they loose happiness/peace the foundation will help them to gain it back.
To conclude there are many ways to attain happiness/peace but actually we need to develop this within ourselves and not by any course