To reject heaven and accept atheism - is not merely about science, facts, beliefs, etc - it is about accepting the reality of all those who have died - being really dead. It is accepting the same reality about everyone you love NOW one day being - really dead. It is accepting the same reality about YOU one day.
The older you are, the more dear loved ones have passed away, the harder it will be to reject the notions of religion. To reject religion requires the re-mourning of everyone who you love who has died.
The complete post is quite long and just as good as this quote.
It's a much older idea than that. One of the best stories on it that I've read is by... Ray Bradbury, perhaps? I'm not sure. It's about a long dead classical composer whose personality and memories are reconstructed inside a living person's brain. He remembers his life, he remembers writing music and even remembers dying... but discovers that he can't compose anything new. Anyone know what I'm talking about?
Go see for yourself.
The complete post is quite long and just as good as this quote.