I have a friend who works as a product manager at a big tech company. He arrived at the office at 8:30 AM. At 9 AM, he noticed chest tightness. By 9:10 AM, his body became rigid and stiff, and he couldn't speak. By 9:30 AM, he was rushed to the hospital, and shortly after arrival, he was pronounced dead from a heart attack. The night before, he had been on a business trip accompanying his boss for drinks and was promised a promotion. Today, seeing Zhang Xuefeng's situation, I couldn't help but reflect. Each of us should understand that our bodies have limits. Many people misinterpret self-discipline as: no matter how busy, you must still exercise; no matter how tired, you can't stop; elevated heart rate is fat burning; chest tightness is just poor condition; less sleep can be pushed through. The issue is that health is achieved through both training and recovery. Overtraining can easily lead to sports injuries and negatively impact athletic performance. When experiencing chest pain, chest tightness, obvious heart palpitations, dizziness, blurred vision, nausea, unusual fatigue during or after exercise—especially the kind that's different from normal—and additionally if there's family history of sudden death at a young age, or you personally have hypertension, hyperlipidemia, diabetes, smoking history, or have recently been sleep-deprived, under high stress, or exercising intensely after an infection, that's when you must stop immediately and seek professional medical evaluation if necessary.