How much practical difference does all this make for the average schmuck who just wants to be a little more fit? Sometimes it's difficult to schedule everything optimally, and sometimes I just like to be spontaneous. Maybe I'm out riding my bike, and I suddenly decide to scoot home and do a bunch of squats. Am I going to either harm my body, or get significantly less benefit for my efforts. I am willing to work hard, but I won't stick with all this fitness stuff if I can't have fun and be spontaneous sometimes. What wisdom from the gurus and pundits of physical fitness?