I cant stop making kids cry. What do I do?

Honestly, I don’t know what’s come over me. A while ago, I accidentally made my 7 year old cousin cry because I was joking around about how she had 1 mistake in her exam. Then her sister told her “Haha you have 1 mistake, you don’t believe in God.” Then I said it again and she started crying. Looking back, that was honestly such a horrible thing to say to a child even if I was used to her calling me mid or making comebacks after a roast I make. I don’t really know what’s happening to me lol.

I also made her cry a few weeks ago because I was playing around with her candy with her sister. We tossed it around for two times and I don’t really know why she cried even when she does that too. And it’s honestly really scary how I can’t even understand or sympathize with how she feels. I can’t even process my thoughts very I act. I don’t think I’m growing up correctly and I don’t know what went wrong. How do I fix this? Do I have to read a book? Watch a movie? Or is this just unfixable and I’ll continue being an asshole for the rest of my life?