"You have to forget your last marathon before you try another. Your mind can't know what's coming." -Frank Shorter (U.S. Olympic Marathon Gold Medal winner 1972)
If I forget my last marathon, then I would never attempt another one.
Its the memory of the joy, the thrill, the excitement, the untold happiness and also the nervousness, the despair, the frustration, the pain that drives me to attempt my next one and to look forward to reliving all those sensations again.