The second, equally devastating approach is to go hard all the time. This is more common in younger riders who think they need to go to their max every single day in order to get better. It is also common in triathletes, many of whom appear addicted to training. The result is a near constant state of fatigue that lulls some people into thinking they are doing all they can to improve. While some will become frustrated about their lack of improvement, most eventually resign to the status quo and believe they have reached their peak.
Here is a nice rule of thumb. Unless you have practiced an activity for 10,000 hours (see the 10,000 hour rule), you can always improve.
In addition to a lack of improvement, ineffective strategies also lead to overreaching, overtraining, and burnout. None of these are good and like so many things in life, it is easier to prevent these conditions than to remedy them.
The key to improvement in training is high intensity. Without it nothing else matters. However, it is important to realize that you cannot perform at high intensity unless you are both healthy and well-rested. Effective training programs will allow sufficient time to recuperate before key workouts.
Exactly how often and how much you should rest depends on your specific genetic makeup and training situation, but if you don't feel excited and enthusiastic before races and key workouts, chances are you are doing too much. Apart from periodic (one to two day) rest and recovery, you also need the occasional long (>1 week) recovery in order to do well and improve.
Yesterday (Wed 3/17), easy 25 mile ride;
Today 12 mile hilly run (the Strawberry Canyon trail loop).