What does a dream about a snake guarding you mean?

The guardian snake in this dream might represent the snake(s) on the Caduceus, which is the winged rod with twining snakes that is the common symbol for medicine. In this case, the dream suggests that you are depending on medical treatment or have confidence in medical science to provide protection from illness.

Alternatively, the snake might refer to "Don't tread on me" flag of the early American Colonies, that currently is popular with the Tea Party in the U.S. In that case, the dream might express your dependence on ultra-conservative values including states' rights and expanded gun use.