Cyclists and runners tend to train only aerobically and only focus on their sport, but by training other energy systems, you can actually improve your aerobic fitness. Mix up your program with weight training, swimming and other endurance activities.
Don't underestimate the importance of a solid nutrition plan, massage, and sleep, either. Think of them as recovery tools they all factor in to help your body bounce back from your intense training sessions.
Finally, decide when it's most important to peak and plan your training around those dates. If you try training hard all summer, you'll end up overtraining and burning out again. Just identify your most important races and schedule your training to peak for those events.