Complex sentence: He claimed that deep down we all retain a belief in our own perfection, and the perfection of anything we are part of, as we mature, grandiosity gives way to self-esteem, and the idealization of the parent become the framework for core values.
Split into simpler sentences: He claimed that deep down, all people retain a belief in their own perfection and the perfection of anything of which they are a part. As a person matures, grandiosity gives way to self-esteem, and the idealization of the parent becomes the framework for core values.