There are many situations in life where you preemptively decide on some course of action, but when you have to actually take that action you don't.

A particular such situation is euthanasia - you might decide that if X happens you want to be killed, but if X actually happens you might not be able to or want to.

Let's say there was a magic pill which could ensure that if X happens you die painlessly, and it's irreversible. Would it be moral to take it? By taking it you, in some sense, murder your future self, which might not want to die even though X happened. However, it's still yourself - I don't see how that's very different from smoking, which would also hurt your future self against their will.

What are your opinions? How do you think you should treat your future self from an ethics perspective?