There are many answers to this, I believe the answer also varies as how you see this question. For me, the most important part of our health is our physical well-being. This means being fit (eating the right amount of food and the right kind of food). Eating too less can cause vitamin deficiency and other problems. Eating too much can cause you to be overweight and ironically just like not eating enough, can prevent some parts of your body from functioning. Also, having enough sleep, sleep helps the cells in our body.