Your surgery went well, and you recovered quickly, so you did not finish the narcotic pain killers your doctor prescribed. When a coworker complained of pain, you thought nothing of sharing a few pills with him or her. Or perhaps a friend was struggling to get through a tough week at school, so you gave him or her a few of your Adderall to help with studying. Maybe you even handed over the prescription bottle. Perhaps you went as far as having your prescription refilled for your friend or coworker.