You just can't "lose" who you are/were. It's like saying that you lost your "2016 self" or something like that. Are you the same person that you were in 2016? Yes and no, movement is inevitable, you may think some things differently, but overall you are the same. Reincarnation and identity are like the ship of Theseus, if we replace all the parts over time, is it still the same ship? I think I proposed many answers during the years, but today at least I think that what matters is how the parts interact with each other, so yes, it would be the same ship.
Back on topic, purposes tend to use several lifetimes, I don't know anything about your past life or "magick", but whatever you have to do I' m sure that goes beyond learning something in particular. Let things flow and see where they take you.