It is difficult to pick out just one characteristic that exemplifies happiness. There are many facets of happiness that vary with each individual. Each one of us potentially has our own unique ideas on what happiness is, and therefore, how to implement a life full of contentment.
There has been a lot of research on the pitfalls of seeking externally for joy. While fortune, fame, and successful careers can complement well-being, depending on them for authentic happiness is a lost cause.
Genuine happiness comes from within. It is important to remember that whenever we ponder over the idea of our own happiness. We have the tools to seek happiness internally and create it for ourselves. There are naturally going to be external factors that add to it, but quite often these factors are more based on momentary pleasures and not the cultivation of long-lasting contentment.