I think that the definition of happiness may be different for different people. Everybody on Earth lends different weights to the aspects of his or her life, thus it's impossible to find a catch-all definition for such a broad concept of happiness. What's obvious though is that the people you'd expect to be the happiest: the rich, the famous and the beautiful, are often not as joyful as you'd think.
In my book, The Post-College Guide to Happiness, the definition I present for happiness is not one of immediate gratification or surface satisfaction. I believe that true happiness has a lot more to do with deeper fulfillment than it doest the accumulation of material goods. Those who are happiest seem to have a life direction that matches up with what they want and love to do. You can have all the money in the world but if you don't enjoy what you're doing, you probably won't be happy.
Another aspect to my happiness definition involves your relationships with your partner, your friends and your family. It's tough to be happy if your relationships are contentious in any of those areas. Even if these people have wrong you it's best to replace your grudges with gratitude. If you focus on the bad aspects of any relationship, it's likely to be unsatisfying. Don't let your negative emotions get the best of you with the loves of your life, cultivate patience, logic and love instead.
Self-esteem is a key part of any definition of happiness. Even if you're doing what you love and have great relationships, a low feeling of self worth can torpedo your happiness. Fortunately if you, like me, were born with low self-esteem, you can develop more over time. Self-esteem is equal parts making yourself feel good about what you do and making others feel good about their deeds. If you start praising yourself for your successes and sharing your gratitude for the accomplishments of others you will begin to feel much better about yourself.
The definition of happiness does not include the word "simple," because achieving a consistent sense of happiness requires hard work. Would you expect to be in good shape if you didn't exercise for a year? The same is true about happiness. If you don't work on it at least a few times a week, it will become flabby. Feel free to take these thoughts (and additional ones in my new book) to create your own definition of happiness.
Done with the Definition of Happiness? Go back to Motivation Techniques.