Excersize is not bad. Just the intensity could be. If your muscles are sore, you should give them a day of rest so they can heal. You do retain fluids in your muscles that help repair them. It can take 2 days for my muscles to release the fluids. If i work out hard on Friday, wake up saturday sore, if i don't excersize saturday or sunday, by monday the fluids are usually gone. The experts do recommend giving your body at least one day of rest. If you are afraid of breaking a routine, just make one day a light, leiserly walk. There is nothing wrong with that. You just don't want to go all "full out power" 7 days a week. If your legs are sore one day, then you should do something that works your arms and abs and back. Then the next day you can do your legs again. But you have to give your body some time to repair itself or you could end up hurting your muscles.
I look forward to reading what everyone else has to say on this.