Athletes in general are competitive animals. In the weights room constant 'pushing' can be detrimental for the following reasons:
1. Technique and form degrade increasing injury risk.
2. Postural changes may actually decrease the stimlus on a target muscle group.
3. Stress on the nervous system is pronounced and can cause overtraining.
4. Equal or greater force can be exerted with sub-maximal loads due to the velocity of movement.
Undertraining Vs Overtraining? I vote for the former, Less is more!