Challenging questions to answer

Someone recently asked, "What about exercise makes you feel so good afterwards, so you want to do it again?" New to exercising, she did not get that feeling of euphoria so many people seem to get. How would you have answered her?

What other common questions, at work, home or elsewhere are hard for you to answer?

What makes some topics easy to answer, while others are challenges?

Please do share your answers and insights, so we all can learn from each other!