And as a follow up, anything done to excess is not good. You can stretch too much, lift too much, run too much. Also, stretching should never cause pain in uninjured areas. And stretching an injured area should be cleared with a physician or physical therapist with recommendations for ROM of specific stretching exercises and the level of discomfort that is acceptable. In general, I recommend that any pain is a reason to stop the stretch in question and consult a professional as to continuing the stretch.