Would tiredness equates, up to a point, happiness?
It does seems to me that the cases of being unhappy and depressed can stem from the lack of activity, rather than a surge of it. Perhaps our preoccupation with work keeps us from the small trivial things that would make us to view our life as pointless... and is that a bad thing?
Is it a case of happy unaware worker and the sad contemplative hermit? I don't think so.
Even on our own, with our mind left to stagnate, we fell prey to all those unhappy and negative thoughts. And it doesn't have to equate not working - even with our hands full, but with our mind empty, the devil comes out to make a playground.
I suppose that's why they say an idle man is the devil's playground eh?
And on a somewhat similar note, ever notice the words those unhappy people use? The ones hoping for something to pull them out of their misery?
Perhaps that's what we get for being lazy. Maybe because misery is actually comfort. To be happy require us to surmount energy and effort. Hence, getting yourself busy and tired may prove to be a good step in gaining happiness.
Which is why I try to keep myself occupied as much as possible. Even in my free time, I'm somewhat of a workaholic.
Because life is all about learning. And it doesn't stop until the day you die.
Now don't just sit there all day and let your mind rot. Do something.