The life of the unbeliever must be truly depressing.
Oh, I know. They will never confess to it. They will say that is we Christians who are fooling ourselves, who have turned away from reality.
But in fact, life without God is pretty depressing.
Oh, not the day to day existence. That you can get by with well enough. Heavens, there are whole days where even I forget that life can be hard. But then something bad happens. A terrible something, a tragedy.
The believer has ultimate hope in both the sovereignty of God over their lives and the assurance that, ultimately, everything will turn out alright. But what does the non-believer have? Nothing. The stark, howling nothing of a universe that has nothing in it but natural laws.
The unbeliever cannot - really - take refuge in anything have a purpose either. In the naturalist world, there is no purpose. There is no karma, no fate. There is merely the actual hopelessness of accepting that ultimately all this has no purpose - in 100 years after your death, you will not be remembered and for most, their efforts and contributions will have been in vain.
Not surprisingly, the believer attempts to whistle past the graveyard. Confronted with actually tragedy, most seem to try to slide around the enormity of the hollowness (which has always struck me as a little odd for those that present themselves as hard nosed realists).
Somewhat surprisingly, most Christians try to assist them in avoiding the issue.
Life without God should be depressing. We need to be confronted with the hollowness of such a thing. But the point is not to wallow in it; the point is to then point people to the One who can give it meaning.