arg your actions in life may still matter to the people they affected or still affect. Your stream of consciousness may cease to exist, but it was never everything in the first place. I'll explain that point. Imagine you were raised in some advanced incubation by robots that all self destructed after you were weaned and they'd left you enough food to get into pubescence. You're stuck on earth like that, with nobody, not even a robot, nothing made made is there at all. Nobody ever teaches you anything, nothing that would require the interaction of another human for you to understand is known to you.
That is not life as we know it, you would naturally resist pain and death, as a living thing, but would you care about that life as much as your own, real life?
Furthermore, would you be able to survive and live happily, if you were transported to a different historical period? Are there historical periods and locations you could not survive in?
The value of life is, once we intellectualize it, attached to our specific culture and the people around us. That's what I think anyway. Maybe I'm just depressed.
I don't know if my points are clear here. Basically life is valuable to intellectual humans because of the specific elements of the society they are in. Without any society or other humans, or with an especially ill-fitting one, it may cease to be valuable to such people. I think this partly makes it rational to care about your effect on people beyond the grave.