1. Have a Plan
No shooting from the hip. Whether you're talking about training, race preparation or racing, always have a plan. Proactive behavior will allow you to know what's coming up, how to prepare more specifically and reduce stress. If you look at successful pros, their seasons are planned out ahead of time. Additionally, they start their preparation for an upcoming event weeks, or even months before.
2. Sweat the Details
A successful cyclist pays attention to elements from the exact timing of nutrition to how long it'll take to drive to an event. Don't take a lax approach to the process. Things like taking food and appropriate fluids on training rides, proper inflation of your tires, packing your bag for a race, post race nutrition, making sure your bike is in good working order, bringing enough money for the entry fee, safety pins if registration runs out, and the list goes on. Being detail oriented will help to insure that you are prepared for every scenario.
3. Rest as Hard as You Train
I say quite often that it takes as much discipline to make yourself rest as it does to train hard. Many cyclists are guilty of not resting enough. That means taking enough easy or off days OR staying within specified training parameters on active rest days (heart rate or power/wattage limits). Not resting "hard" enough will eventually create a situation where you can't train hard enough. Training is about intensity and if you can't generate the appropriate intensity, you won't reap the corresponding physiological benefits. Additionally don't short yourself on sleep.
4. Don't Overthink it
While the above-mentioned elements are part of the key to success, don't get overly mired down in the details. Over analyzing every single watt, kilometer, calorie or hour trained or slept will drive you insane. Keeping a training journal allows you to put all this info in a central location where you don't necessarily have it spinning around it your head. Have trust in your plan or your coach's plan. The last and most successful of the Samurai warrior culture, Miyamoto Musashi, said one of the keys to his success was that he didn't think two moves ahead; he lived in the moment of the battle. Try not to focus as much on the outcome; instead look to the process itself.