This is a very simple principle. If you surround yourself with positive things, you will naturally be happier. If the previous statement is true, you should consciously make your surroundings more positive. Think of it in two ways. First, by being kind to people around you, you will feel satisfied and get more social energy. Second, when you give happiness to other people, they will give happiness to you naturally.
This is the social aspect of it; however, there is also a physical one, which is making your environment more positive, like spending more time in places that make you happy.
Surround yourself with positive people.
You will get more social energy from them.
Make your environment more positive.
Spend more time in places that make you happy; for example, in parks.