I think that Goethe is suggesting that individuals have and must use their own sense of freedom and autonomy in defining their identity. This is a highly Romantic idea, in which Goethe believed. Individuals cannot expect their past to fully define their own sense of self. The Romantic thinkers were strong advocates of self definition, of utilizing one's freedom to break the shackles of social conformity. Goethe is arguing this point. What has been inherited from one's parents is good, but if one simply lives their life through this, one is not living their own life, but rather the life of someone else. Reflect on it in this manner. If someone inherits a large sum of money and they don't do anything to add to it, then they are not living their own life, but the life someone else has given to them. Their life, their sense of being, is not their own. On this level, Goethe is saying use what others have given you, but stand on your own and carve out your own identity so that one's life is one's own and not the extension of someone else's.