Hello! You posed a great question! In my travels through life I am a mix of Catholic by upbringing, Buddhist by study to temper my upbringing and Yaqui Indian in practice. But please hear me out.
How I understand karma is as if each and every one of our actions are like throwing a pebble in a pond. (common anolgy, but it is perfect.) Those closest to us are affected the most deeply and this changes a small part of them. Good and the bad. What they believe, what they want, how they behave because of who we were and what our example meant to them. We have all been inspired by others in the past and they changed who we were and our tragectory in life. Then a secondary ripple follows to those that come into contact with those you have changedfor the better or worse. Depending on what happened. The ripples keep moving outward. Keep in mind this isn't a one way street, this is happening to us and to everyone else in a mind-boggling complexity. And so on and so on as the ripples flow away. Of course the more potent the actions, the greater magnitude and circumference that it reaches. Good and bad. These actions...THIS is karma. (Let me build on that.)
In comes my science degree. So when we die our energy, our former life force does not inhibit one specific creature in the future. We are particles of energy that are taken in by living beings that need nourishment. They grow, thrive, live and we are a part of them. But it is energy only. Our energy returns to nourish the flora and fauna and we are given rebirth in so many new organisms through our body are being nourished to live in a world...though
Reincarnation certainly exists. But to trace it backwards that we were something or someone specific is our own ego telling us there is a holistic transformation. Our ego wants us to believe that we are preserved and moving forward as a singular organism because we are special, important. Actually we are! But not like your self-preservation instict is trying to convince you of so it stays alive. And that is truly the only reason it is telling you that, to stay alive. You are a speck in a speck of time. You are a special snowflake. You really are. Be glorious! Be you! Change the world!
Karma is how our decisions, our choices while in our current consciousness made those ripples. What is left behind to shape the world for those creatures we are will be a part of of once we die...again. Our energy never dies. What we do with it never dies. What we do with it is what we will be a part of for as long as this masterpiece continues.
Be the artist your are right now. "Be the change you want to see." Because when your bodily energy returns to the universe and melds to create new creatures in their many forms it is constrained by the life you have helped shape for their future.
Losing the sense of self goes beyond the grave.
In my humble opinion.