Is Emerson really saying "believe anything you want to believe and do anything you want to do"? Is he really saying "Nothing outside yourself matters"? Explain!
The short answer to your question would be yes, Emerson is saying that nothing outside of yourself matters (in his essay "Self-Reliance"). One may have an issue with this based upon rational thought, but this is what Emerson relied upon when making the statement.
Basically, Emerson is saying that people have the right to think for themselves. Based upon this, people should not be concerned if society will approve of the person's actions. That being said, Emerson is not leaving morality out of the equation.
Instead, Emerson bases his ideology upon the education of man and their belief in God. Men, who believe in God, would be sure to only act upon thoughts and decisions which uplifted God. These actions would be made based upon their own individual uniqueness and the fact that they were put on the earth to perform unique acts.
In the end, Emerson is simply stating that people need to trust in themselves.