To get something closer to my intent, imagine an external party giving you a choice to either give your past self a message (both the message and the past point in time being of your choosing), or not. If you decide not to, nothing happens, but you won't be asked again. If you decide to actually do it, then your past self receives the message and you become your past self.

There's little opportunity to quicksave under such a scheme :) One couldn't deliberately plan a virtual-immortality idea either... though I guess the "cost" could be made less if the message is sufficiently long - just say things like "try to befriend these people, it'll be worth it".