"No pain, no gain" is an impaired mental state diametrically opposite to the manner the best of the best train and compete. Inflicting self harm: stressing your body to the point of pain, injury, and illness is not physically, mentally, nor emotionally healthy. Training ideologies based on "PR or ER" are cancerous & result in athlete's blowing up, melting down, or burning out.
Mental Training – TED talks
Amy Purdy: Living Beyond Limits
Mel Robbins: How to Stop Screwing Yourself Over
Alison Ledgerwood: Getting Stuck in the Negatives (and how to get unstuck)