Becoming active is a positive step that will improve your health and the way you look. Even exercising as little as two days per week will yield results. If working out two days per week is good, then going six or seven days should be even better. Unfortunately it doesn't work this way. Benefits from exercise are only seen up to a certain point. Going beyond that without being physically ready can cause what's known as overtraining which will reverse any gains you've made.
There are plenty of warning signs leading up to a full blown case of overtraining. As you workout harder and harder without giving your body the proper time to rest, your muscles begin to get injured which causes weakness at first but can lead to more serious injuries.
Normally you have on and off days. During on days, you exercise and actually cause small tears in your muscle fibers. This sounds bad but the damage is fixed on off days when you rest.
During repair and recovery, the muscle is made bigger and stronger. If you keep working out and never give your muscles the time to heal, they will always be damaged and never get stronger. The result will be excessive muscle pain and weakness. The weakness will result in bad workouts in which you will no longer be able to hit your full potential.
Another major sign of overtraining is getting the common cold more often that you normally would. It has been shown that a moderate level of exercise can help make your immune system stronger. Increasing your exercise beyond a certain point (that is different for everyone) will weaken your immune system and cause you to get sick.
If you notice that you're getting sick too often, it could be due to excessive exercising. Overtraining can also cause you to be tired and lethargic throughout the day which will not only affect your time in the gym, but also your day to day activities: work and school.
Too Much is Bad
Even a good thing such as exercise can be taken to an extreme and cause a reaction that is opposite to what you're looking for. Aches, pains, plateaus and getting sick are all signs that you're pushing yourself too hard.
The Bottom Line
For the best gains, start your routine off slowly. If you feel that you're pushing yourself too hard, take a step back (a few days off) and continue where you left off. There's nothing worse than being forced to stay at home by muscle pain or a cold when you though you were at your peak.