On being happy

So I'm just plowing through work today, mentally checking off one task after another as my body scrambled to actually put into action the flood of "gotta get this dones" and a random thought popped into my head: "I'm feeling pretty happy today."

So then I have to go and ruin it and say "Why?" Which led me to think about happiness in general, and my versions of it. I know when something pleases me...for instance, I'm never so occupied and content as when I'm in my home office with the tv on (most likely to an episode of Law & Order or HGTV), a cat on the monitor, puppies at my feet, full drink at hand, puttering with files and webpages and all matter of electronic ephemera.

Which begs the question, why do I feel so gloomy and miserable when I have the above scenario to return to, basically at my leisure? I mean, I have an obligation to be at work when I'm required to be, but even that isn't so bad. So what causes the general melancholia and moodiness? Is it really a jinx on the happiness if it is acknowledged and appreciated?