The Buddha is recorded to have said, "We are born of our Kamma, related to our Kamma, abide supported by our Kamma. Whatever Kamma we shall do, of that we shall be the heir." Normally it is taught, the moment of death is an important time to decide what happens after that moment of death. If we are able to collect our mind at the moment of death and have a beneficial mind state, then it leads to the rebirth of a beneficial state for ourselves. If there is not enough time to do that, then it is taught that our habitual Kamma will take over. Say for instance, a person is in a coma and is not aware then habitual Kamma takes over. Another example would be if a person has dementia then their habitual Kamma takes over.
So it is quite important to develop an awareness of death, reflecting that it may come at any time so that our last thought is not, "Why?" or rejection, or "Not now!", or "I don't want this!" We may not have a choice at that time as it is our Kamma so being able to focus the mind on something beneficial would be skillful for us.
It is also quite important to learn how to resolve past memories that we may not wish to look at in our life. If we can resolve them and if these memories arise, we won't have regret that may influence our moment of death in an unbeneficial way. Learning how to do Compassion/Lovingkindness for the people we have been in the past, learning how to forgive ourselves, see the changes, see the differences and that we are not a solid ego that continues and accumulates. We need to develop the capacity to see that the person we used to be and that the person we are now is different. That the person we used to be, didn't have the understanding, the compassion and so on, and caused suffering for themselves and others. We can learn to have compassion for that person and forgive. Learning to see the changing nature of the ego helps greatly in letting go of regret, guilt, all these painful memories that have an emotional charge when they arise. Gradually the memories can lose their power to throw us off balance and it just becomes a memory rather than something that gets us spinning around in self-hatred or doubt or other negative mind states.
So learning how to resolve our past with a lot of Compassion/Lovingkindness meditation and Forgiveness meditation, helps to prepare ourselves to die. By preparing ourselves to die, we live more skillfully here and now. Some people think that this idea of preparing ourselves to die is morbid, but learning how to reflect on death teaches us how to life, how to deal with the past, how to resolve issues, how to appreciate what we have now and our loved ones. It teaches us how to live effectively. And if we can use death in a very beneficial way, through skillful reflection on death, then it helps us understand what is important in our life and what is not.