To continue the topic of how much is too much OR what should I add in or take out of my practice, here is another article that talks about the matter from MindBodyGreen.
Over exercising is an epidemic right now. In some respects it is the new diet fad. When we over train our muscles or cardiovascular system for long periods of time, it puts wear and tear that can be detrimental. It can take a long time (years?) to re-build a healthy system.
We encourage you to stay grounded and present in your fitness practices so that you don't go too far.