Our bodies our minds are designed for activity, they are made so that we can work hard and then rest and repair.
Without movement the structure and body systems deteriorate and soon become a shadow of what it once was, a beautifully organic self repairing machine.
With movement however, we thrive, our neural pathways have greater feedback, we have better control over our bodies, we stimulate and push our bodies to heal and repair. We circulate more oxygen and nutrients, hormones flood and flush our system and make us feel good, making us stronger and full of energy.
Why would should you let anyone make you accept - "By doing your exercise or sport you'll always have pain".
Question it, challenge it, ask the community for advice...