It does not have to be hard to be good - Each workout is part of a larger picture. If you put their backs to the wall in each training session you will quickly lose sight of the big picture. Everything must be in context. Remember that different physical qualities adapt at different rates, so they need to be stressed differently. One workout cannot make an athlete but can break an athlete.
Too much, too soon - You can’t hurry the adaptive process. The younger athlete can handle a lot both in terms of volume and intensity, but if you lose sight of the big picture, it is important to remember that by not following proper progression and individualizing can stifle long-term development.
Overloading the spine, too often and too young - Even with the mature athlete the spine just cannot take the heavy repetitive loading that is imposed on it by too much heavy back squatting and dead lifting. That does not mean you don’t use those exercises, just use them wisely.
Too many exercises or drills in a training session - This just leads to confusion from an administrative perspective and poor adaptive response on the part of the athlete. This results in a loss of focus. They get tired but they do not get better.
Repetitious Exercises - This usually overloads one area or one component; the result is a poor training response. I always say hunt with a rifle, not a shotgun.
Training to failure - This leads to failure. Each workout becomes an end unto itself, and the athlete starts holding back anticipating the failure thus dulling the ultimate adaptive response.
Over reliance on one exercise or training method - This creates a one trick pony. Highly adapted instead of fully adaptable. You are what you train to be.
Reliance on a machine in training or a modality in rehab - You adapt to that environment; it is an artificial “safe” environment but not the environment you need to perform in. Sport performance occurs in an information rich dynamic environment.
Quick fixes - There are none! I have learned that a quick fix is an easy come, easy go proposition.
Crash programs - Crash programs eventually crash, probably sooner rather than later you can’t hurry the process. Adaptation takes time and the time frames for the various components are quite predictable.