Religious beliefs come in different packages. In most cases, a belief in the nature of "After Life" drives a lot of the mythology, rituals and practices. These specific set of beliefs in the nature of afterlife can drive daily decisions around how to live life, and even how to end it.
Three flavors of afterlife: Belief in afterlife also comes in three flavors. Read the Wikipedia entry for more details, but given below is my simplified argument. So, as I was saying, belief in afterlife comes in three flavors- (1) this life is all there is to "me", (2) I have only one life, and my fate after life will be decided by my actions in this life, and (3) This life is one in a series, and over many lifetimes I will be able to achieve a state where "I" will be extinguished/salvaged.
Belief in afterlife comes naturally: If you read my previous post, you already know that I recently suffered the loss of my Father. His loss made me realize how "extended narrative" was a very natural conclusion. It is very hard for the mind to accept that someone who was there today, will no longer be around tomorrow.
Filling in the blanks: When we close our eyes to blink or think, our brain naturally assumes the continuity of the world around us. Most optical illusions are based on this quirky feature of brain wiring- that we "fill in"things that we assume to be there. It's probably the same thought process that makes us continue to think that the departed person, or at least the "essence" of that person, continues onward much after their death. The mind "fills in" the departed person, refusing to recognize that there will be no more real interactions with this person.
What if this is it? There is, after all, no real scientific evidence of a "soul" or the continuity of a personality after physical death. If a person subscribes to the view that there is no afterlife, would their behavior be designed to make the maximum out of this life, or to think of life's objective as being the "propagation of one's gene pool"? All non-human living beings, I suppose, belong to this school! Because we can, we humans spend our life thinking about the purpose and meaning of life. To be a lifelong pleasure seeker, or to be concerned only about the propagation of one's own gene pool, even these are choices that require some thought about the true meaning of life.
One shot, that's all! What of those who believe that this life is just a short prefix to an infinite afterlife, and that our actions in this life determine our comfort/pleasure in the afterlife? Then, I suppose, people would make some stark decisions about how they want to lead this life. They could lead their life fulfilling a set of action and "Requirements" laid out before them so that they may be judged well. They could, on the other hand, think that this life is but a means to an end, and all actions are justified (however irrational or inhuman they may seem), as long as they are convinced that they are promised an exciting after-life in return. Both choices- a life of piety, or a brutish, short life of inhuman action - both these choices can be made by adjusting "the beliefs" to manipulate the behavior of the individual.
Many life-times: Modern video games come with multiple lives. You could lose one life, and still carry on your mission regardless. Somewhat like this is the Hindu/Buddhist believe that we are trapped in the Samsara- the cycle of birth, death and rebirth. In this belief system, a soul could be reborn into any living form, but the ability to act and do something is only present in the human birth. The objective of the human birth, therefore, is to do enough good work to be reborn a human being and, through geometric proportion acquired over many lives, tote up enough karma points to buy an exit from this endless cycle.
This belief, of a single narrative extended over multiple life-times, is very prevalent in Indian culture. Some of the "let it go" mentality in India comes from this- what's the rush!? People trace relationship and interactions over several life-times. All good and bad fortune can be explained away through this extended narrative- I must have deserved this fate because of actions in my past lives. This belief in an extended narrative makes people more likely to accept their current situation.
The United States, on the other hand, is a society that acts like it believes very little in the afterlife. Everything has to be consumed now,in this lifetime. Every whim has to be pursued now, in this lifetime. Nothing must be left for later, to another lifetime.
Extending the argument a little, could it be said that most of the wars and conflicts are started in this life, but continue because of the difference of belief in the afterlife?