Known has Hebb's Law or Hebbian Learning, the now famous phrase "Neurons that fire together wire together" was first presented by Canadian neuroscientist Donald Hebb in 1949 - 67 years ago!!!! His visionary understanding of a key aspect of what we now call Neuroplasticity is considered the basis of all learning. Neurons that co-activate will do so automatically with repetition... which is why it is not so easy to break a habit once you make it. Some "bad" things need to be "unlearned" in order for new "good" things.