The whole point of this essay is that people need to rely on what they themselves believe and not on what society wants them to be. Included in this idea is the idea that people should not be materialistic.
The quote you cite promotes this view. It argues that society tends to judge people based on their material goods. This does not encourage people to be who they are. So when you base your self-worth on property, you give in to society and you lose sight of your own more personal values.