Go outside in the sun every day or
Get some GOOD full spectrum natural light bulbs in your house where you spend most of your time with the lights on
You can find out which kinds are good here
Sunlight is essential for so many factors of health, healing and life.
The way I look at it is like this. Life on the whole planet is dependent on the sun, we are part of nature and the planet and so are we.
You need sun on your skin and in your eyes without chemicals, sunglasses, contacts, windows or the such in between you and the sun.
Concerned about Cancer? You should really check out chapter 9 and 20 of my book, The Creators Manual for Your Body - Freeing you from the Bondage of Symptoms and Disease for Life.