It a very old saying which we have been listening from hundreds of years. Modern lifestyle doesn't give us ample time to maintain a good healthy life.
We can discipline ourselves with following rules:
1. Sleep (6-8 hours)
2. Food and nutrition (Low carbohydrate, moderate fat, enough veg or animal proteins, healthy food)
3. Activity (physical and mental) walking, exercise and sports, readings books or social media
4. Holistic approach to life: Spirituality, share and care, honesty and healthy thinking