If naturalism (atheism) is how reality actually is, then life is a tragedy. We are the accidents of an impersonal universe. Our lives have no meaning or purpose—except for the arbitrary purposes we create—and everything we do will be ultimately forgotten and inconsequential. We’ll be forgotten—along with everything we every do—and we will not continue to personally exist after our physical death—we’ll be become dust and cease to personally exist. This is a tragedy. We might inject humor into our lives, but the most consistent approach would nihilism.
(Thanks to Glen Scrivener for helping me think through these kind of categories. Check out his book).