The way the Buddha teaches mindfulness of death makes sense only in the context of his explanation of what happens at death.

"The way the Buddha teaches mindfulness of death, it makes sense only in the context of his explanation of what happens at death. If it were the case that death were the end of everything, mindfulness of death would mean doing everything you can to survive physically and squeezing as much enjoyment as you could out of whatever time is available. The attitude of “eat, drink and be merry, for tomorrow we may die”: That’s how some people think about death.

But as the Buddha pointed out, a basic principle of mundane right view is that here is the next world, and it’s built by your karma, built by your actions. And as he explained further in transcendent right view, your state of mind is going to be very, very, important at the moment of death. You want to be able to see your clingings, see your cravings. If you can learn how not to ride with them at all, so much the better.

But if you find that you can’t manage that, at least keep yourself, as the texts say, “rightly directed.” Have a sense of what would be a good rebirth, one where you can practice. But always keep in the back of the mind that even places that are good to practice have a lot of dangers."

~ Thanissaro Bhikkhu "Mindfulness of Death & the Deathless"