Long distance running requires a lot of stamina and mental strength. Some people say it is relaxing.
How can it be relaxing? 
Well, humans are well adapted for running significant distances so I think once someone does it for a while they get use to it and it becomes something they like to do.
How does it help one mentally? I could use some help, I have mommy brain. 
I'm not sure I couldn't find that but, I do know that Long-distance running is only considered long distance if you run at least over 5 miles
How do you get started with long distance running? 
You have to pace yourself. First start out with smaller distances like 1 mile, 2 miles, 3, etc. Eventually you'll get to continuously running over 5 miles and once you do that it will be easy.
Do you need special shoes for running?
consist of only a thin sole and simple strap and be sold for a low cost. High fashion shoes made by famous designers may be made of expensive materials, use complex construction and sell for hundreds or even thousands of dollars a pair. Some shoes are designed for specific purposes, such as boots designed specifically for mountaineering or skiing.
Traditionally, shoes have been made from leather, wood or canvas, but in the 2010s, they are increasingly made from rubber, plastics, and other petrochemical-derived materials. Though
Long-distance running
Long-distance running, or endurance running, is a form of continuous running over distances of at least 3 kilometres (1.8 miles). Physiologically, it is largely aerobic in nature and requires stamina as well as mental strength.
Among mammals, humans are well adapted for running significant distances, and particularly so among primates. The endurance running hypothesis suggests that running endurance in the genus "Homo" arose because travelling over large areas improved scavenging opportunities and allowed persistence hunting. The capacity for