Heart Rate
A wise man once told me that if you take your heart rate (HR) each morning you will quickly get to know your resting heart rate (RHR). If your RHR is above the normal level (ie RHR is normally 45 and its 50 or above) then you are either stressed, haven’t recovered effectively from the previous session or you are over trained. Either way, listen to your body and take it very easy and have a rest day.