How do you define happiness?

So what is happiness?
Is it simply a smile on your face that lasts through the day? Many believe they know the answer to this question.. but is there even a definition? How can there be a sentence to describe an aspect of life that is so easy to achieve, and yet so hard? Can joy be over-looked? Can you choose NOT to be happy? And why would you?

There are so many things in life that make you wish, dream and yearn for ecstasy. When you get into an arguement with a friend, when you lose someone close to you, you seem to sink into a sea of despair. There doesn't seem to be a light at the end of this dark tunnel you've chosen to follow through with. But yet... you find that one thing, or that one person or that one memory..that suddenly makes it all better. You're suddenly happy. You're laughing, smiling, and believing in yourself all over again.

So the definition of happiness? Maybe it's waking up in the morning in a warm comfortable bed. Maybe happiness is realizing that there are people in the world we live in today striving to make our planet a better place. Maybe it's laughing till you can't hold back the tears of mirth. Maybe happiness is the giddy feeling you feel in your stomache when you realize you're in love. Maybe happiness..can not be defined.