My story won't shut up

I did my absolute best. I wrote a story, let it sit for a month, spent several months pouring over every detail, handed it to my critique partners, edited some more, sent it to Betas and put it through two more rounds of revisions.

I called it done.

And now here I am, two months later, and my story won't stop talking to me.

My characters won't stop talking CC

I wrote the sequel to my story during FastDraft. I never imagined re-awakening my characters would create such havoc in my head. I'm supposed to start editing book two today, but I can't. After all, there's no point working out the finer points when there are changes going on in the first book.

This was my first time writing a sequel so I had no idea to expect this. Is this normal? Has anyone else ever had a story that won't stop clamoring for attention?