The necessity of a workout plan is put in place so that you cannot over train yourself and you cannot overstrain your muscles. There is no way you can build muscle when this happens. The way muscles grow is through training and resting for muscle recovery. That means you undergo proper training by lifting weights that are just right for you. The weights should be neither too light nor too heavy to lift. Once the muscles go through the right load of weights, the build muscle are flexed to its maximum so that muscle damage occurs. It is necessary to have muscle damage to allow the release of growth hormones. If overtraining happens, your body cannot repair the muscles even with ample sleep and proper nutrition. Or if you do not give yourself enough sleep and you go through another phase of weight lifting, the damaged muscles having been deprived of recovery will be over strained and over trained. Muscle growth will not happen in this case and your weight-training program will not be successful.