It is very important for long term success in running that you don't train too hard. Even though running hard is the best way to improve, it isn't realistic for most people who have a life, job and family. Training hard leaves you without the energy to maintain your normal schedule. You need to throw your ego out the window and listen to your body.
Kids are great examples of how to run.
They run until they feel like walking, then walk until they feel like running, and so on. Pretty soon, they are able to sustain a moderate pace. When you decide it is time to run hard, make it for a short distance or time. Make sure you know the difference between the interval days when you whole intent is to improve your pace and your easy days that are working on your aerobic base. It is very important now that you are used to the impact of running that you spend your time running easy for longer periods of time to help develop your aerobic base.