When I was 9 or 10, I started realizing that all books had happy endings. 
Before, reading was so real for me: I would get scared for the characters, and feel like I was in their world.
But then, I started to notice that their lives always turned out perfectly. I started hearing people say, "Life doesn't always have a happy ending." But it did! At least in books.
I would start to be disappointed because I always knew the main character would be safe and happy by the end of the book, so what was the point of reading the story if I knew the ending?
Even now, when I watch TV and the plot is very sad, I know it's all going to work out for the characters.
And in my life, things usually seem to work out in the end.
So I pretend I'm in a book, and I'm the main character: nothing can hurt me, because it will work out in the end.