In time, the religious see their versions of reality as reality, creating a delusional world, deceiving themselves and—for those who proselytize—deceiving others. One of the aspects of life that seems to perturb and displease these people the most is the corollary of birth: death, something that we're all gonna have to deal with some day. These deluded people are discontent with the likely possibility that death is nothing more than eternal unconsciousness, a notion that I don't think is difficult to accept. Roughly, consciousness exists because of sensory organs and the brain that processes infiltrating nervous impulses; when those are completely destroyed—when the means by which consciousness is sustained cease to function—consciousness ceases to exist, and that's it; it's not a hard concept to grasp, but religious people can't handle the simplicity and finality of that explanation and respond by saying, "That's too simple; there has to be something more to all of this," when they're really just saying, "Reality is boring; let's make it more fun by fabricating uncorroborated claims and present them as truth."
Some argue that those who believe in an afterlife took up that belief because they are afraid that death is really "the end." I argue that certain religions are able to create a fear of death. Most religions that incorporate an afterlife in their doctrine present two posthumous possibilities: reward or punishment, Heaven or Hell, among the most popular of these religions are Christianity and Islam. Because eternal punishment is seen as a possibility in the eyes of adherents to certain religions, these people are forced to deal with unnecessary anxiety and guilt caused by the fear that they will be sent to Hell for things that are usually really trivial and harmless, like looking at porn or being gay. Atheists, on the other hand, are not faced with such a fear, but instead faced with the realization that death will in all likelihood be a state of total, perpetual peace devoid of consciousness, judgment, reward, and punishment, which to me is a fuck of a lot better than living with undying uneasiness over what's going to happen to me after I die.
Whenever a theist tells me that I must live a depressing life, not believing in an afterlife, thinking that death is really the end of it all, I have to set them straight and say that I actually think my mindset gives myself and others a more positive outlook on life. As I said before, some people who believe in an afterlife are severely terrified of the thought that they might have to endure eternal punishment, but there are also some people who stare death in the face with extreme happiness and can't wait to die because they think that they might fly up to Heaven and experience eternal bliss. These kinds of people look forward to that afterlife more than they look forward to their current life, which is really the only life that they know they're going to get; they look forward to death, and that, to me, is a depressing mindset. I think the acceptance of the notion that you probably won't get an afterlife makes you appreciate the life that you do have a lot more, and it motivates you to live your life to the fullest, in addition to eradicating the fear of eternal punishment and the fear of eternal reward. Most people don't see eternal reward as discomposing, but I do because—as the late Christopher Hitchens pointed out—eternal reward is just as indicative of a celestial totalitarian dictatorship as eternal punishment is. Being conscious for eternity, whether I'm being rewarded or punished, is a thought that scares me shitless, so it's refreshing to know that there's no reason to believe any of this religious bullshit to be true.
To conclude, I find belief in the afterlife to be a nonsensical, unreasonable, irrational, unnecessary product of wishful thinking that has the capacity to be very emotionally damaging, and I would advise whosoever holds this belief to drop it. I would advise anyone who holds a belief that goes against reality just because reality upsets or bores them to drop that belief, but it's not my job to tell other people how to live their lives. If you want to deliberately dwell in a reverie and adhere to archaic, delusive, apocryphal, illogical make-believe stories because you lack intellect and the courage to accept reality—if that's your thing, then good for you. Just know that it's impossible for me to take you seriously or have any respect for you on an intellectual level.