The secret is wonderfully simple. Just enjoy yourself. Of course, if you are unhappy and all of your energy is expended on something you don’t enjoy or something that ultimately creates more stress than pleasure, your immune system is going to suffer.
The power with which your body can fight off illness is directly related to the level of stress in your life. The more panicked you are in your everyday life, the more energy your body expends being stressed, and conversely, the less energy you have to fight off illnesses.
Another very simple way to maintain longevity is to keep nature as a constant in your life. Keeping plants in your living space relieves air pollution and pumps your environment with fresh oxygen. Living in rural areas, close to wilderness also correlates to a longer life.
Wanna live past 100? Try keeping it simple, and living in harmony with your environment.