Aim to finish your workouts feeling as though you could have done more and reward your body for the work it has done with adequate rest and sleep. During sleep is when the body repairs itself. Without adequate sleep, fitness is lost and your muscles breakdown regardless of your training program. If this cycle of inadequate rest continues, injuries occur. First you may experience discomfort that comes and goes with activity, and then it may become more persistent. It is important to have the injury looked at as soon as you experience the occasional discomfort to ensure it doesn’t result in you missing out on weeks of training.
Good luck in the upcoming season! I hope to see you at a race.