When I sold my first book back in the Dark Ages, my editor, Leslie Wainger, asked me if I had tried to have two projects going at the same time. No, I told her, I have to finish one before I start the next.
"Better learn," she told me.
Excellent advice. Some editors are really fast. They can turn around every aspect of a project in a very short time. Others work more at the pace of a hibernating bear. If I hadn't done what Leslie said, I'd be somewhere back around book thirty instead of somewhere around eighty.
It's not always easy. You can't just turn off the faucet on the big-scope, layered women's fiction, then turn on the faucet for the tighter, more intimate romantic suspense and expect it to flow. There's a transition period where the water trickles out about as clear as mud, and I'm pretty much stuck until it runs clear again.
Thank God, eventually it does run clear again!