Structured training is all about repetition and specificity. In executing a training plan, we're throwing specific and repetitive workload at the body in order to convince it to make physiological adaptations. In basic terms, the desired adaptations are increasing the body's ability to do work for longer and at higher intensity for reduced physiological cost.
Think about the last time you thought it was a great idea to do a Century Ride and your most recent long rides haven't exceeded 30 miles. Your body ends up protesting quite a bit, you stay sore and fatigued for much longer than you anticipate. By the time you feel good enough to train again you don't really benefit from that workload because it took you past your preparation.
We can go scientific on this subject in a longer article. The big take away here is about trusting your plan and structure once you've decided to commit to a training plan. There are days to go full gas with high intensity. There are days for long rides pedaling at a high quality endurance pace. We need to also maintain high quality focus on the active recovery rides and complete rest days. Again the idea is to apply the appropriate level of load with intense training and volume with the long endurance days in order to fatigue and confuse our bodies. Then on the active recovery and rest days the body has the chance to regroup and make the physiological changes we have provoked during the training days.
Dave