Memory

Some people have good memorys. Some have great ones. The other day I was talking to a few friends about skin spots. I mentioned that I have a spot that looks lighter than the rest of my arm. One friend said that it was the spot where I burned myself. When did I burn myself? I had no recollection of a burn. She said that a few years ago when I was cooking, I leaned against a pan and burned my skin in the exact spot that is now lighter. I did not recall doing that. The more she said it, the memory started to come back. This was at least five years ago. Why did she remember it and I did not? I can remember the minutest detail of unimportant things so why did this slip my mind? That question will remain unanswered.