Every single person is different. Some can tolerate more exercise than others so making one rule for everyone is close to impossible. Most guidelines recommend at least 3 days of exercise per week and not more than five or six.
When you exercise, you cause quite a bit of damage to your muscles. The whole point of exercise is to do this damage while giving your body the adequate nutrients and rest it needs to rebuild and repair. When you rest, your body goes into the damaged muscle and start fixing all the damage you've caused. When it's done, the repaired muscle will be stronger than it was before.
If you do this over and over again for months and years, you'll get stronger, faster and be in better shape. If you exercise too much, your body will never be able to fix itself and you'll continuously see yourself getting weaker and slower.
While exercising is the catalyst for improving, resting is when the real progress happens. When you first start out a routine, go slow. Begin by only exercising 2-3 times per week. After your body is used to that, increase it to 3-4 times per week and finally 5 times per week.
If you ever start getting overly sore or your workout suddenly seems lethargic, your body is trying to tell you to take a rest. Some athletes can exercise 6 and even 7 days per week with an adequate amount of food.
The Bottom Line
Even if you are working out 6 or 7 days per week, not everyday is going to be at a 100% intensity level. There's a huge difference between doing sprints and walking around the block. While being sedentary is bad, so is exercising too much. Like many things in life, you need to find a good balance.