Our perception of reality is different from everyone else, yet everyone else has an incredibly similar perception of reality. This leads us to accept certain truths, such as the fact that we all breathe air or perhaps that jumping off of a tall enough building will kill you. Over time, more truths are accepted, and we experience new things that seem to be just as true as anything else.
If you take a look at history, it's surprising to see how little humans have changed other than our technology. That's simply because we have all shared two simple truths throughout the existence of Earth. Life, and Death. We haven't changed much because it's easier to just continue what works, and it's even easier to look at how people from past generations have lived up until their death.
As I said earlier, we understand the basics of life and death. I am alive, and some day I will die, and that day could be any day. However, this presents a problem: We have only ever experienced life, which most of us are contempt with. Also, those who have died can't share any information with the living, that is, if they experience anything after they die. Also, most of the ways people die or the experiences leading up to death are extremely painful. All of these factors combined have lead us to believe that death is not as good as living, and probably the worst experience that we can endure. ( I would go into how religion and faith tie into all of this, but that usually starts an unpleasant experience. )
