Let's concentrate on that then - I'm inclined to believe that some theists - Christians in particular - fear that life is without purpose, and
then we die and there's nothing after.
Personally, I don't see life as having any purpose beyond what you make of it - in which case, I'd much prefer to make the most of this life, rather than banking on there being something better waiting for me after.
That way, if there's something after - score! I've had a great life, and I can enjoy the afterlife. If there isn't - score! I've enjoyed the one, single, purposeless life I've had, and my body can decay in the ground and the cycle of life continues.
I quite like Professor Brian Cox's take on the afterlife anyway. He deems it impossible because of the laws of thermodynamics. Humans are essentially "heat engines" - in order to do work, we require heat energy, and we get that from processing food, and similar.
Once we die, we can no longer process food, so no energy transfer takes place, so we do no work. If no energy is being transferred, then no part of us can live on in the afterlife. If humans have such thing as a soul, the laws of the universe dictate that we'd still need energy in order to power it. Our dead body isn't making that energy, and nobody else is... so there can't be an afterlife.
He sums it up as saying that if he died and found himself in heaven, he'd then have to ask, "well... how do refrigerators work then?!", since fridges operate on a very basic principle of thermodynamics - to remove heat energy from the inside of the fridge, the elements at the back must be hotter than their surroundings, transferring heat away.
If there's an afterlife, then fridges have to be impossible.
Think about that next time you're making a sandwich