We forget we have a choice of focus. Yes, we're tired; yes, we work hard. But the tiredness is well-earned, the working hard allows us to feed and clothe ourselves, to rest when we can. Illness means our body is working toward health; restlessness means we're halfway there.
I get it. It's so easy to go negative because it's always, always there--maybe it's a side effect of gravity? But even at our most blissful, our most in-flow, the negative is there--we're just too well-balanced, too much the masters of perspective to let it bother us, to let it pull us down.
But if we can remember those moments--those balanced moments--even if we can't pull ourselves into them, then I think we'll get a window into what it will be like when we finally accept contentment as our natural state.