Each season, an athlete should have a purpose, a goal, and a reason for all the training. One or all of these are usually centered on an important race or set of races. The high priority races are established at the beginning of the training season and always seem to be approaching rapidly.
Most athletes have enough motivation to drive themselves to train hard day after day.
The challenge that I run into as a coach is trying to get them to balance that motivation with enough patience to assure they get adequate amounts of rest. Without that rest, their bodies won't be able to recover from the days, weeks, and months of accumulated training stress. Gains in fitness are the result of both training and rest. Without training, the body will not be stressed enough to cause the adaptation that will make it stronger. Without rest, the body will not be able to recover from that stress and will eventually become so overloaded it will begin to lose fitness.