Always plan your training to progress gradually, roughly at a 10% increase (mileage) per week. It is also very important to mix up your training containing a mixture of high and low intensity levels.
Plan recovery days into your weekly schedule and consider a weekly break every 6 weeks. Furthermore, sleep is incredibly important for our recovery so try to encourage 7-9 hours sleep per night if you are training hard or have stepped up your frequency/intensity.
3. Strength and Conditioning
Spend some time strengthening the key muscles that you are using during your sport. In addition you should consider cross training once per week, which involves completing an alternative activity to promote muscle recovery and also fire up different muscles to overall keep you stronger and fitter. For example, a marathon runner would benefit from cycling or swimming at least once per week.