Heroism that involves facing death would not be so heroic if the hero felt completely certain of a good afterlife. But given the close rational connection between the existence of God and posthumous rewards and punishment, a connection that is also emotionally ingrained in us, for it to be heroic for us to face death a certain hiddenness of God appears necessary. The hiddenness would only need to be emotional: God's existence (or love or justice, I guess) would need to feel uncertain. And of course what goes for heroically facing death also applies to more minor sacrifices and obedience to the moral law.
Such a feeling of uncertainty, however, is compatible with a rational moral certainty. One can, after all, have a feeling of uncertainty and the associated fear while stepping back into the abyss on an indoor climbing wall despite moral certainty in the safety of the equipment and the competence of the belayer. So this need for emotional hiddenness doesn't solve the Schellenberg problem of hiddenness which is about belief not feelings of conviction. I wonder if it helps in any way? After all, one way to ensure emotional hiddenness is by having doxastic hiddenness.