Why you need a Coach!
Coaches can be the difference between the development of a good athlete and a great athlete. They can structure your training and lead you to optimal training. Which of course leads to great results!!
Planning:
When planning a season self-coached athletes always tend to do more than they can actually handle and usually getting injured. A good coach will structure your training correctly to make sure you are getting enough adaptation from it while also keeping you injury free. They are also experienced at planning seasons and knowing how to get you in peak condition come race season.
Signs of over training:
There may be a few sessions per week where you and your coach meet up for a session (typically key sessions and not just easy runs) as he watches you run. A good coach can tell if you have been over-training based on how you look and feel as you run. He can also pull you out of sessions when you are so tired your form is out of control.
It is always better to leave a session giving 90% then giving 100% and getting injured. A self-coached athlete usually drives through the pain to get the optimal adaptation but is counter-intuitive when they get injured!!
Group power:
Training with a coach usually also means training with multiple other people who are also coached by the same coach. Coaches usually gives the same level athletes, training for the same purpose/race the same training sessions. Training in a group is much more motivational then by yourself and can push you through workouts you thought you couldn't do!
Overview:
Coaches can really spur on your training for many reasons! It is important to trust one you believe in, as when you trust the coach you trust yourself come the big races. It is important to be clear to your coach and let him know your goals for the season. If you believe in the coach and trust the process he puts you through thats when the magic happens!