The American Declaration of Independence in 1776 claimed 'the pursuit of Happiness' as one of the 'unalienable Rights' of 'all men'. The Founding Fathers were very wise. They did not attempt to define what they meant by happiness. Nor did they claim that anyone had a right to happiness, only to pursue it. But happiness doesn't want to be pinned down. The more we pursue it, the more elusive it becomes.
Today, I'm back where I started. I don't think happiness is an emotion. At least, if it is, it's not like other emotions. I now know that the nature of happiness is a hot topic of discussion among psychologists. And they can't agree about whether it's an emotion, or a mood, or something else. So I feel happy about having my own feelings on the subject. One of the problems with naming things is that there are just not enough words to go round. The word happiness is used for several different concepts that are essentially different. It's always much easier to borrow a word from something else than to create a new word... especially when the thing you want to identify is as ill-defined as a feeling. Perhaps we should take a look back in time and see how we got into this situation... linguistically I mean.
The root of happiness is the medieval word hap, which meant chance or luck. This chance connection is preserved in modern English in words like hapless and perhaps... and even the word happy in the phrase 'a happy coincidence'. In nearly every European language, the word for happiness originated in the word for luck. The German word for happiness is Glück, which can also mean luck. But the medieval concept of hap was a bit different from our modern idea of chance. The first man to describe himself as 'happy' knew nothing of probability and had never heard the word risk. Hap was something that just... well, happened.
So, we can see that historically happiness was associated with uncertainty. And yet we believe that somehow we can strive for it... pursue it. Even more thought provoking is to look at the etymology of sadness. That's the opposite of happiness, right? The word sad comes from sated, which means to be full up, to have all desires satisfied. Sometimes we imagine happiness to be the state in which we have everything that we want. But it turns out that's the definition of sadness! Perhaps certainty is not such a good thing after all.