So many good points to respond to... Not possible to do you all justice, so I'll touch upon things as best I can.
@Lynn: The glass is always full -- sometimes liquid, sometimes air, but always full of potential.
@Carina on knowing rightness: I tend to think that we should follow the scientific method as best as we can, even in informal settings. This means we should test and verify repeatedly. In so doing, we never actually arrive at "right," but we can gain increasing confidence in workable models, and equally important, we can discard models that fail in the face of better evidence.
@Niall on zones: see
And I'm always happy to discuss it further.
@Graham: I very much like your calculus of depression/happiness. The idea that it's a matter of vectors rather than points makes sense to me. It's complex, though, and Carina correctly points out that sometimes just being where you are is true satisfaction.
Yet acceptance also has its zone. Acceptance is a boon where we can arrive at serenity in the face of truly unalterable circumstances. At the same time, there is a risk of fatalism in acceptance which can be contrary to well-being.
Very nice discussion. Thank you all.