https://youtu.be/tB_fDYj7of8

One of the most healthful things we can do is go outside, and preferably into nature for a while: the edge of a forest, an ocean or lake shore, hillsides, or otherwise. This stands to reason, because Homo sapiens Sapiens is a creature who matured for thousands of years outside. We know the risks and hazards of a sedentary life, and the current quarantine makes our situation even harder. This is a big reason that the City of Fullerton needs to preserve as much of Coyote Hills as possible: for nature trails, for the wildlife and plants, and for the oxygen a green area creates. Most of Orange County is "citified" now. 

More on this subject from the American Psychological Association: 

https://www.apa.org/monitor/2008/03/outdoors