Disturbing Dreams

Why do people have disturbing dreams? I spent the entire night last night having one bizarre dream after another that I awoke from covered in sweat. Truly terrifying dreams - dreams you wouldn't wish upon anyone - WHY? I hate having dreams like this as I wake feeling uneasy and then find out someone has died in the family - truly creeps me out. I'm hoping and praying that all family and friends are all safe and sound and ALIVE this morning.