I am seventeen and am in complete denial about my limitations

Being self aware about this denial is a great start to accepting that you do have limitations. I'd say staying busy and feeling that your 'invincible' is fairly common for many teenagers. Nevertheless, have you ever tried meditation, tai chi or yoga as a avenue for slowing down. Deep breathing exercises can be key to being present and in the moment. "To Know thyself" Just 20 minutes a day can make a difference.