I agree that you need to push yourself to your limits often in your training (especially during intervals), but doing so every single day you run can put you at risk for injury unnecessarily. That is, assuming you're running more than 3-4 days a week. Your body just can't recover quickly enough to be pounding it in an all-out effort every single day, especially if you haven't built up a solid base of easy running. Believe it or not, there is something to be wrought from long, easy, hour-long runs, and it's more than just the feel-good aspect of it.