Slow and steady wins the gains
You have to give your body time to rest--your workout shouldn't be so draining that you need more than a day or two of rest inbetween.
Most workouts should be done at about a 6 out of 10 effort so that you're not over exhausting yourself but still getting some work in.
If you're going to high intensity work outs then they should be done in short intervals. That's the way they're designed to be done anyway.
Your workouts should leave you feeling a little buzzed and hyper as the endorphins kick in. If you've worked past that point you've gone too far.
Don't exhaust yourself so much that you lose form. This is how you hurt yourself.
Are you getting stronger or faster? What areas need improvement and what areas can you leave alone for a little bit?
Go at your own pace, push your own limits, remember it's not a race.