Religion teaches people that this life is only a blink of the eye, a tiny moment in which we get to decide if we’re going to be happy or miserable for the rest of eternity.
Naturally, people who take this seriously, take qualifying for the next life very seriously, and take actually living this life less seriously. Dreams can also be put off for later, when you’ll have a world better than your wildest dreams. Opportunities can be passed up; you’ll always have more, and much better ones in heaven. Anything which jeopardizes your chance of heaven must take supreme importance, and everything else must fade into the background before it.
Naturally, this gives us less of a reason to pursue the full potential of this life, to suck all the marrow from the sweetness of our world, and to make of ourselves all that we can.