It's saying our brain determines who we are (our personality, our thoughts, how we interact with the world). When it says ".... that makes you become yourself" it is suggesting that who you are now (your personality/behaviour) is a result of ever-changing changes to our brain throughout our life. Good and bad experiences shape our brains and this in turn shapes our personality and makes us become "who we are" - how we perceive the world and they perceive us.

This statement means that the brain holds the components to make an individual who they are. The brain is a powerful thing. It holds our memories and experiences. It absorbs information, and it is how we observe and learn behaviors. The components in out brain makes us who we are. It takes the brain to generate an individuals personality, and it takes their brains to make life decisions. Each person has unique experiences and they process experiences in life differently because of beliefs, upbringings, and what their societies deem as normal. Our brains are constantly learning and absorbing even when we are not making the effort to absorb.The human brain is a remarkable machine.