Walking, parks, brooding.

 "Brooding, which is known among cognitive scientists as morbid rumination, is a mental state familiar to most of us, in which we can’t seem to stop chewing over the ways in which things are wrong with ourselves and our lives. This broken-record fretting is not healthy or helpful. It can be a precursor to depression and is disproportionately common among city dwellers compared with people living outside urban areas, studies show."

http://well.blogs.nytimes.com/2015/07/22/how-nature-changes-the-brain/