A life without festivity is a long road without an end.
Yes, you know him mostly because, with his mentor Leucippus, he came up with the idea of the atom. But he was also known as the Laughing Philosopher (because he engaged in round mocking of human inanity), and as you can see from the quote above, he didn’t believe in being dour. He was a well-traveled man who was insatiably curious about the world, and became respected by his contemporaries because he understood the natural world well enough to predict some happenings in it. Some of his ideas on the origins of worlds and their eventual end are eerily prescient – we now know that bits of matter colliding is what forms planets, and that collisions between worlds can, indeed, destroy them. I expect if we could transport him to the present, he’d get a kick out of modern cosmology, which in these respects has largely proven him right. And he’d have plenty of human inanity to laugh at.
So, heed the wise words of Democritus and go have yourselves some fun.