[jlgreco]

I would say that a message coming from my future sell would probably be treated differently than a message from somebody else in the present. Unfortunately, that "treated differently" would probably involve my past self seeking psychiatric attention.

You could say something to your past self that would verify your identity in an attempt to make your words carry more weight, but I don't think there is much you can do to convince a past self that you were not a figment of their imagination.