> If I get used to being physically active, the next day that I am NOT physically active I feel terrible. How hard are you pushing it? Increase the difficulty

> If I get used to being physically active, the next day that I am NOT physically active I feel terrible. How hard are you pushing it? Increase the difficulty/duration, and you may find a different outcome. I'm not talking pro-athlete level, but competitive high school athlete level (2-3 hours / day, 5-6 days / week, with some good lung heaving moments each day). > On the other hand, if I have been lazy for a period, then one day I do a very brief exercise, even a 10-min moderate run, makes me feel excellent. However when I start doing those runs everyday, I don't feel that same good feeling. I don't think this is the opposite. One is moderation of laziness, the other of physical activity. "If I'm lazy for a week, the day of exercise after that lazy week is more enjoyable".