Monitor physical exertion to avoid fatigue. I use a heart rate monitor to keep my heart rate from creeping up and ultimately overexerting myself. If I see my heart rate is getting too high, I take steps to lower it before I fatigue.
I’ve talked about this in detail in a series of blogs on How I Eliminated My Leg Cramps. See the following posts for more details.
Judging My Physical Exertion,
Knowing My Maximum Heart Rate and
Lowering My Heart Rate