An Attempt at Definition
What is happiness?
To start, most people would reference well-being and contentment. For something so vague, “well-being” and “contentment” are adequate, so let us build upon this.
In valuing our state of being, there are two extremes: In [Definition 1], we define intrinsic targets (e.g. certain levels of intimate relations, social interactions, influence and material wealth) and judge ourselves to be happy when we meet them. In [Definition 2], we survey the lives of our peers, and bind our happiness to how much better off we are.
Quite clearly, the latter definition is unfavorable—if we take being happy as being above the mean (of human existence), then a great deal of people will never achieve consistent happiness. I would argue that the majority of us judge our lives against those of others. It is simply the easier route—who wants to spend time determining some arbitrary standard, and will themselves to be “happy” when they meet it?
What do we do then? For one, we can lower our expectations. If we were all content with the 25th percentile rather than the 50th, a fourth of the world would be happier (as is quite obvious). When we shift that down to the 0th percentile, Definitions 1 and 2 begin to merge, in that happiness now becomes independent of all environmental factors (i.e. autonomous).
However, it is not reasonable to believe that we can live as islands. Instead, in drifting to Definition 1, we can choose moderation in all ways (I am quite partial to the Epicurean conception of ataraxia) and choose to be happy.
This is my definition:
Having satiated the physical, happiness is a state of mind to be seized.