Throughout this fascinating essay Emerson makes it clear that in his mind, the antithesis of self-reliance is civilization because it encourages conformity. Note what he says about the negative impact of civilization and how it encourages us to relentlessly conform:
These are the voices which we hear in solitude, but they grow faint and inaudible as we enter into the world. Society everywhere is in conspiracy against the manhood of every one of its members. Society is a joint-stock company in which the members agree for the better securing of his bread to each shareholder, to surrender the liberty and culture of the eater. The virtue in most respects is conformity. Self-reliance it its aversion. It loves not realities and creators, but names and customs.
Here we clearly see why, in Emerson's opinion, civilization is so dangerous. In solitude we can hear the "voices" that tell us to "trust ourselves". Civilization drowns out those voices. Society itself is designed to "surrender the liberty and culture" of each member as we all conform together towards one common goal. Society loves established "customs" and "names" rather than the more creative "creators" and "realities". To be truly self-reliant, therefore, Emerson seems to be saying, we need to distance ourselves from society and civilization so we can trust ourselves.