I found that knowing what to do, how to do it and how much one has to do at the right time is essential.
Training too hard
Training too hard, too soon and one reaches a deeper level of fatigue which requires more time to recover and making it impossible to reach targeted peak period with a higher level of base fitness. Unbalanced, continuing to push through and one is I'm on the path to becoming over-trained and coupled with inadequate rest the risk of injury and illnesses is high. Eventually performance drops, and if deciding to carry on by increasing workload or not taking a break will result in chronic fatigue. As a result the mind and body is exhausted to a point where a decrease in training or a few days rest makes no difference.
Training just right
Induces manageable levels of fatigue that is easy to recovery from, requiring a smaller amount of time ensuring that one is able to reach desired and targeted peak fitness and improving base fitness as well as maintaining and or improved levels of motivation.
The "just right approach" when combined with a tailored training plan creates a balance, allowing you to be physically and mentally rested, and repeating this method of training will ensure a steady progression towards a goal.
Training too easy
If the workload is too easy, time taken to recover is short as the level of training fatigue is too low. The body is not optimally stress and as a result minimal and a short lived improvement in base fitness is achieved. The target period can be reached by adjusting, however the level of performance achieved will be insufficient.
Have a goal, know exactly what it is you want, your goal must have an end towards which your passion, purpose and effort is directed to. Establish your current state of fitness by doing a specific test and use the data to determine your training zones.
Know and understand your unique abilities and formulate a personalised plan that maximize your strengths and stretch your limits, then train and rest consistently within the plan's guidelines.