What are some signs that you are over exercising and under exercising?

Well,...: As you would expect,...overexercising may cause you to get sore, have rapid heart beat, become fatigued from too much exercise, get short of breath, etc. Under exercising would cause you to remain out of shape, possibly continue to remain at the same weight, possibly have high cholesterol, and essentially not achieving the benefits you would expect from exercising.

Effort not exhaustio: For most people, a good exercise level that gives conditioning benefits are when you are breathing heavier but where you can still comfortably carry on a conversation with a friend. Also, at the end of exercise, ideally one feels exhilarated and energized and not totally depleted or exhausted. However there are many caveats and exceptions depending on the individuals health and exercise goals.