[dexwiz]

Of course the only me that exists is right now. In no feasible reality would I ever shake hands with me from yesterday or me in the vat. Nor would I ever shake hands with me in a robot, just a robot that thinks it's me. Even if those other entities exist they are not me.

[anon-3988]

Except you don't treat them that way. You feel sorry about your old self. You feel sorry for other people, even though you cannot prove that they even "exist". You care about future you even though it doesn't exist.

Unless you don't.

I agree with your conclusion that because that is the reality of life, the only time worth spending is right now.