Diolch yn fawr! I credit my grandmother. She taught me (aged 4) to use phrases I knew were correct such as “I’m going to…” and “…with me?” to extrapolate what slightly more complex phrases like “X and I are going to…” and “…with X and me?” ought to be. I’ve applied that kind of “What do I know for sure? What might follow from that?” thinking to language ever since. (And very, very rarely have I ever got and I/me wrong, LOL.)
So, this is me doing the “be like a child” thing SSi recommends, I guess. 
I love that it reminds me of her.