I think the problem I've been having lately is that I'm not really having 'rest' days. I'll do 1-2 workouts a day plus or minus some activities (volleyball, hockey). What are peoples thoughts on rest days? How many should I have?
It probably depends on the intensity of your workouts and what you want out of exercise. I've heard that for building muscle you should have at least one day in between workouts (but if you focus on a particular group one day you could do another the next). For cardio I'd probably just try and work on how you feel, if your muscles hurt right at the start (or even before) you exercise then you might be overdoing it, if everything's fine then you've probably got one of your days where the exercise you're doing is light enough that your body can recover from more intense workouts.
My plan is to keep at least 1 day free a week because I really don't want to injure myself from overwork and end up having to take weeks off from everything to recover.