A book that was written for parents and educators about this phenomenon is Last Child in the Woods by Robert Louv. Granted, it is more about the effects of nature on children, but the same can be said for adults, as well. Learn about scientific research that proves the power of nature. It also provides a wealth of activities for you to do on your own as well as with kids.
Another book I reviewed a couple of years ago is Connecting to the Power of Nature. It is a somewhat New Age-y book, but the stories in it ring true. Joe H. Slate, Ph.D. takes readers through a series of anecdotes that demonstrate the power of nature and then provides exercises you can do. If you can get through the fancy words, you will fundamentally find a way to become happier as a person and to reconnect with yourself as you explore the Great Outdoors. Read my full review here.