When you get into a distance running program, you are lucky to stick with it. Now that you have made it through 2 months, it is time to become an expert in how to stay with it long term.
Muscles work it two ways, eccentrically and concentrically.
While running, the backside of your legs work concentrically to propel you along and the frontside of your legs work eccentrically to allow you to land smoothly. The more you run, the more you will realize the importance of stretching. I don't concentrate on it early in a training program because of information overload and stretching can be detrimental if done too much or when you are sore. You spend a lot of time sore and adjusting to new workouts when you start a program. When you are sore and tight, it is very important not to try to stretch before you are warmed up.