HERE is an interesting video on how our beliefs have become instilled throughout history. Hopefully, you will find this very illuminating.
Your core beliefs can change drastically during your life. A serious situation can arise at any time, which demands that you re-evaluate those beliefs. For example, if you lose a child, you would most certainly be devastated, but such a terrible event would most likely cause you to re-think your beliefs on death. Is there a God, did angels come to greet your child or is he or she just gone forever? A death in the family is by far the biggest factor that determines whether your core beliefs will stay the same or change in some way. Another reason you might change your views is if you are in a life-threatening situation yourself, such as a car accident. Some people even have a near death experience that completely alters their beliefs.
For a more comforting video, please enjoy This One by John Lennon: