Snake in a dream symbolizes negation.
To dream it can mean that you are in negative situation, but still you are denying it. It is possible that such dream is a reminder for you to stop lying for yourself.
Also, it can indicate that your insightful thoughts are blocked right now. Thus the dream is just a subconscious representation that you are stuck in a negation and thus you need to rethink your actions in order to overcome current obstacles.
Negation symbolism in a snake dream can be seen as prognosticating good luck, because of insightful message that it carries.