Haven't read the thread, so apologies if this has been mentioned.
Also, have to say, it's interesting because I've thought about this a lot recently (cue self indulgent liberal).
On morning talk radio in WNY area they briefly touched on this by quoting/referencing some comedian (you all likely know him, I don't follow comedians at all, he was in a car accident and almost died, can't remember his name).
This guy said (paraphrasing) "Happiness is having something to look forward to".
Kind of an innocuous statement but it always struck me as kind of profound. It will mean something different to different people but examining my own life it rings true.
It becomes harder and harder to find those things it seems as you get older. A lot of simple tedium it seems.