Heavy lifting takes a lot of energy and mental readiness. If a long stressful day doesn't have you in that zone, resort back to high-volume, lighter-load training. "High-volume training (meaning more reps and sets) has been shown to be as effective as lower-volume, heavy-load lifting. It never hurts to switch up your routines and do something different, so on days when you are tired, give high-volume a try," said Chadwell.