One can eat healthy, exercise, and have total, perfect mental health, but no, in today's world of pollution, toxins,radiation, infectious agents, and trauma, it is not a possibility. There are however things one can do to reduce exposure to unhealthy variables. Eat a balanced diet with fruits, vegetables, legumes, and whole grains. Wash fruit and vegetables carefully. Use unsaturated oils such as canola or olive oil. Cook meats at high temperatures to kill pathogens. Wash hands often. Do not demand antibiotics from your doctor, and if prescribed take for the entire time prescribed. Practice safe sex. Do not smoke. Drink alcohol only in moderation and do not drive if your judgment or reflexes are impaired. Exercise. Do things which you enjoy. Get enough sleep. Get a pet. Spend time with people who make you feel alive and happy.