Why as a kid, everything that happens seems to be life and death?

But then when you become an adult, you laugh at all those "near death (or even heartache) happenings"? And then you tell your children not to worry, when it's only going through the same old cycle? Heck, when you're 17, and the "love" of your life has broken your heart, it seems so big. But maybe, there is someone else out there. How do you look past the "now" and hope for the "future". If this is making any sense :D