A long time ago, before I bought the property I'm in now, I used to walk. I had a friend I often met, but sometimes I just went alone. NJ has some beautiful county parks, and one near me had a large rose garden. Another had an iris garden, and several had lakes. In NJ we pay high taxes but we get much in return.
I experienced what the article mentions, meaning the sense of well being. It is the difference between a good day and a great day. The rest of it I kind of have naturally, but it's hard to tell because I replaced walking with gardening. One thing a person gets with walking that one doesn't get with gardening, at least in an isolated location where I'm at, is people watching. That can be fun, and especially watching kids in the playground. In the town I used to live in, there are many eccentric characters, so I miss seeing them, too.
The article explains the more upbeat mood of a friend of mine. This person is very, very smart and is highly educated. His personality tendency, however, is to be cynical and kind of negative. He doesn't expect positive outcomes. About 8 months ago he started walking and I see a change in his personality. He still has the same personality tendencies, but the "bite" is out of them. Reminds me of what natural remedies like herbs do. After taking them a while, one might still have the same condition, but the intensity of the condition is diminished to the point where it isn't much of a problem anymore.
This friend walks every day--every single day--even if the weather is bad. If it's rainy, it might be just a short walk. When I see him he tells me of interesting things he's encountered on his walks, such as crazy drivers and that some people in our neighborhood let their cats out at night. (We don't see the cats in the daytime.)
I think gardening pretty much accomplishes the same as walking, but not everyone is into gardening. Gardening also requires a good deal of heavy lifting, tools, and money, whereas walking is something anyone in almost any condition can do.