We all try to be pleasant to each other on this Forum, so please don't start arguing in your first discussion, RG59. People are only wanting to help.
In answer to your question, I think that when walking in the countryside, we are free to wander at our own pace, in the open air and with no need to concentrate on bumping into people or thoughts about crossing roads, etc. Whereas, in built up areas, our brains have to work much harder and consider others around us and how we are going to get from A to B. Because our minds are working more, it could cause the feelings you describe, as we are more tense. I have exactly the same trouble and I'm sure many others will agree.