The brain mechanisms that do this are special. That may explain why the first time we do something is always the hardest. Good or bad, the more we do something, the easier it gets. Brain patterns are physically established like wheel ruts in a dirt road. Actually, it's electrical, like building a path of least resistance.
Neurons fire tiny electrical charges to build circuits.
Either way, barring a brain illness or injury, the brain doesn't cause behavior. It changes with behavior, reacting to our own experiences and decisions. Sometimes those physical brain paths get very strong, very quickly. They could be a natural talent for music or a sport, or changing metaphors, the brain ruts could become an addiction like gambling or a bad habit like promiscuity or homosexuality. There is evidence, a mountain of it, that indicates sexual orientation is a choice, although sometimes not a conscious one.