Me thinks you would have already gotten it and spend your life telling someone that you will do that in the future, and then eventually do it. However the burden of proof would suck because no one would believe the message is from the future and when you do send it back it in the future it wouldn't be a surprise since you've already been telling people about the message. I do think however if it was an important one with grand implications the changes would have taken place around you as you pass through time, rendering the need to send the message unnecessary because the point would have already been made. Time travel is ultimately a paradox when considered through the subjective.
Reality objective is merely a collective of the subjective perspective ~Mr Blue