I can't make things up all the time, so I use my memory sometimes. My memory, I have always felt, is kind of crappy, so when I come to use it, I always have to invent that it works fine.
One can't simply wander around the world inventing stuff, in the same sense that one can't simply stay in a dark room remembering names. Creativity is the art of saying that thing that has been said one hundred times (by other people or by yourself) differently. Memory is the art of saying that thing that has been said one hundred times (by yourself or by other people) identically.
I always force myself to remember that I must be making myself up all the time, as my memory is so crappy.