I agree that we should not let the world shape us because it's constantly changing. When people do this, we can see that the impact is usually negative. For instance, a murderer or a rapist might justify his actions because he/she was raped as a child, or lived in an abusive household which hardened them to the point where they have no idea what empathy is. On the other hand, there are those who have been exposed to terrible things, but despite their environment, they chose (with hard work and persistence) to not let that shape who they are or determine their future. Like you said, it should be matter over mind.