New neural pathways are formed as a good habit or a bad habit develops. This is because an action that is performed over chemically alters the brain’s communication system. This is an ability in the brain called neuroplasticity, which regulates learning processes and helps us to adapt to our surroundings. The neuroscientist Donald Hebb claimed as early as 1949 that neurons that frequently fire together form a strong linkage; “neurons that fire together, wire together.”
The more we travel the path, the faster, easier, and more familiar that path becomes, and at the same time wider, smoother, and easier it becomes to travel. It may even become a preferred route. Which is a good thing if its positive thoughts, but bad if its negative thoughts, as e.g. in an addictive habit.