I'm actually more moved by the sacrifice of a mere mortal who is trying to improve things by sacrificing himself/herself, than by someone who believes his sacri

I'm actually more moved by the sacrifice of a mere mortal who is trying to improve things by sacrificing himself/herself, than by someone who believes his sacrifice will not really be the end; And I have a really hard time to see things the other way around, in fact. Actually, I never managed to understand this: if one believes souls are eternal and virtue is rewarded in the after-life, then any kind of sacrifice seems cheaper and virtuous behaviors get closer to self-interest. How to reconcile morality with such beliefs?