If happiness always depends on something expected in the future, we are chasing a will-o'-the-wisp that ever eludes our grasp, until the future, and ourselves, vanish into the abyss of death.
We cannot hope to die peacefully if our lives have been full of violence, or if our minds have mostly been agitated by emotions like anger, attachment, or fear. So if we wish to die well, we must learn how to live well: Hoping for a peaceful death, we must cultivate peace in our mind, and in our way of life.
I think we never become really and genuinely our entire and honest selves until we are dead--and not then until we have been dead years and years. People ought to start dead, and they would be honest so much earlier.