If you get philosophical, I don't think you can really know anything about anything. However, in practice I have every reason to assume that I have been practically dead i.e. non-existent for the vast majority of the lifetime of our universe (and whatever universes there may have been outside our one, whatever that may mean.) And I do not recall being non-existent that bad... Dying, that's another thing, that I know nothing about and am not looking forward for it - quite yet. But I know that the amount of things I want to do here is finite. And based on knowing myself and the feelings of quite a few old people, I am quite sure that when those would be done, I would be happy to let go. (Only small thing that I might want from approximately infinite life, would be to know how this life story here on earth/universe ends.)