As a child of the 1970s, I couldn't hold a narrative in my head; I was lucky if I could hold a joke in my head, because every time you turn on television or radio, it wipes the slate clean - at least in my case. After I gave up television, I found I could carry longer and longer stories or ideas in my head and put them together until I was carrying an entire short story. That's pretty much when I started writing.
Chuck Palahniuk