AS I understand it, the idea of Karma is roughly equivalent to the idea that whatever a person thinks or does comes back to that person. I sure hope that's not the case --- and so far, it doesn't seem to be.
I remember when I was young. Yes, I know that was a loooonnnggg time ago --- but I remember it. And I absolutely did not care for old people. What I considered "old" back then was 35 or 40, people who could easily be my children (or even grandchildren) now.
Of course, I didn't talk back to old people or show them open disrespect --- that just wasn't done back then. But I didn't like old people, and I sure didn't want to stand up and let one sit down on a crowded bus or such (I mean, I was tired, since I had been so busily doing such really, truly important things; why was that old person at home, sitting in a rocking chair on a porch someplace? Why'd I have to get up and let him or her sit down, when I was on the bus first? Sheesh!).
Now, I'm old. Very old. And I remember all too clearly how I felt about people who were older than I was --- but younger than I am now (I'm not sure I really thought that people got to my present age). Most young people don't treat me the way I wanted to treat old people back when I was young. In fact, most do exactly the opposite --- and it annoys me to no end for them to scramble from their seats on a bus and offer to let me sit; "You can sit here, Pops," they say. Pops? Yo' mama...
So...maybe there's something to the idea of reincarnation, and I'll get mine in another lifetime. But I hope not. I hope I'm never treated the way I wanted to treat old folks back when I was young.