You can reject theism, but I am not positively sure what comes after that.
As Marilynne Robinson has pointed to, we are either nothing or nearly everything.
I mean, you have to base your life on something and eventually address the ultimate question.
Is all of this worth anything?
These are not small questions with insignificant answers.
And I just prefer to believe that humans matter.
I think we matter more than you or I can imagine.
Here the simple thought from Chesterton rings so powerfully: When belief in God becomes difficult, the tendency is to turn away from him—but in heaven’s name to what? When Jesus asked the twelve disciples closest to Him whether they too would desert Him with the rest of His disciples, Peter replied for all of us down through the ages when he said, “Lord, to whom shall we go?” (John 6: 68).
-Ravi Zacharias and Vince Vitale, Why Suffering?