There is a way of liberating oneself from the din of petty and mundane difficulties such that one is palpably and profoundly gratified by the fact that this world exists and the fact that one is alive in it. I experience this gratitude often and every day, and it is always present as a backdrop to the course of mental events that offer both din and tune, rhyme and rancor. The backdrop depletes and deadens the din and the rancor by depriving them of their habitual sustenance: attention, concern and valuation. The backdrop is perspective. This is the perennial wisdom. (You can find it most emphatically propounded in Chuang-tzu, though also most eccentrically.) Certain meditation techniques can accomplish it.
It's amazing to me that one can be this happy. I can't see how I am not the luckiest person who has ever lived, even though I know it cannot be so.
But Chuang-tzu eccentrically neglected the virtues and good form: ways of life suited to beings such as we and therefore inextricable from happiness. He failed to see that the backdrop must be a backdrop to something worthwhile if the scene is to amount to happiness. One's actions must be good and one's virtues flourishing if one is to be happy. Certain meditation techniques can create the backdrop of supreme gratitude. Both the areteic and the gratitudinal components are necessary for happiness.
There is a theological aside here. To whom is the atheist grateful? To no one, of course. Use "glad," instead of grateful, if you like. By "grateful" for this world and one's life, I mean glad and joyously humbled by them. Neither is a God to whom one is grateful entailed nor is He ruled out. It's a theology-neutral analysis of happiness.