One of the most important things I've learned while doing this is do not let up after a tough workout. Yesterday I did a high intensity workout for the first time in awhile. It was hard to get up this morning without feeling some pain.
But the pain was from being sore and not hurt. In the past whenever I felt this way I always figured "well this hurts now, might as well take a few days off." A few days would then turn into 3-4, then to a week, then to not even going to the gym.
Certain parts of me were sore this morning, that's for sure. But I still knocked out 30 min of cardio. It helped loosen up some of the parts that were sore, but it worked out other parts as well.
The key is knowing the different between sore and hurt. The one time I ignored being "hurt" I tore my calf during a half marathon. If you are hurt, rest and rehab. If you are sore, don't be a wuss and get back out there.