How to Stay Happy?

I read a story yesterday and let me tell you about it.

When I was eleven years old, God gave me a gift of happiness. One day, on my way home from school, a truck ran over me and cut off my legs. As I lay there bleeding, I realized that I might have to live the rest of my life without legs. How depressing! But then I realized that depression won't get my legs back. So I decided not to waste my life feeling depressed. When my parents arrived at the hospital, they were shocked and sad. I told them, "I've already accepted the fact. Now you also have to get used to this."
Ever since then, I often see my friends getting worried about little things: their bus comes late; they get a bad grade on a test. But I just enjoy life.
I was lucky to realize that it is a waste of energy to focus on what you have lost, and that the key to happiness is to take pleasure in what you have. Sounds simple, doesn't it? So why are many people unhappy?

People often think happiness is based on what you admire. "My whole life would improve if I had a new car." But when you get the car and what happens? Days later you want a new house. Then you go right back to being unhappy.
Happiness is not a happening; it's a state of mind. Maybe you are still unhappy though you have whatever you like. Or you can have relatively little and feel full of joy. Happiness comes from mastering the art of appreciating and consciously taking pleasure in what you already have.

[Excellent.]