It can be difficult. I've lived with these characters for years now. They've gone from initial scribbles in a notebook to feeling like real people to me. I've laughed with them, cried over them, loved them, wanted to murder them. Have murdered some of them... but now, it's time to open a new notebook, fill up a fountain pen and start living with some new people.
Many years ago, I wrote a short story that was selected for the book "Almost An Island (An Anthology of Fife Writers)". The story was called "The Writer" and in it, the characters from a writer's book emerged from the ether in her head and into reality. They were physically real and started to badger her about the plot of the book. They didn't like what she was doing and wanted her to change it all. The book reflected how I feel about my characters. They become so real to me that they do talk to me. They do want to change the plot (sometimes for the better, but not always!) and I do feel bereft when their story is finished and it's time to focus on someone else.
My head is a crowded place a lot of the time, full of characters nagging at me. I write to get them out of my head and onto the paper because (mostly) they shut up then. Although, that then just leaves a space for someone new to fill.
Ah. Yes. Who is shouting the loudest at the moment? Summer and LB from their next book? Finn and Reagan from The Trilogy? Or James and Anna from another thriller?
You know... they're all being pretty loud and obnoxious right now, yelling, "My turn! My turn! Me! Pick me!"