a quote by Greg McMillan:

“Bad workouts and races — we all have them and we always will. Accept that the body has an ebb and flow that we don’t quite understand. Some days you just feel ‘off.’ As hard as it is to accept a bad workout or race when there are valid reasons, it’s doubly challenging when there appears to be no reason at all. I used to worry about this, but now I just shrug it off as the quirkiness of the body and mind. Don’t invest in it or over think it. Move on.”
Greg McMillan, in Gibson’s Daily Running Quotes