A truly incredible run also has a sadness to it. While experiencing the transcendence of that elusive flow state and sense of wellbeing, there is also a reminder of the fleeting nature of joy. In the back recesses of the mind there is a realization of the impermanence of it all. Shortly the miles will end and the flow will cease. You will be left having tasted splendor, but will be unable to retain it. You will inevitably and naively try to conjure up that awe during the next run, but only leaden legs will respond. These runs are existential teases.