Kate Wilhelm’s book, Storyteller is chock full of good writing advice as well as providing a fascinating look into the generation and survival of the Clarion Workshops. I'm reading it slowly to savor it, and I recommend it for new and used writers. (I’m including myself in the latter group.) In chapter 1, Wilhelm stresses the need for a writer to set aside a regular time to write, and to keep that time sacred.
To keep writing time sacred means protecting it even from those who love you and are just trying to help. Even for those of us who write a lot, this is something we can forget. I also hurt my soon-to-be ex-wife’s feelings pretty badly once over this exact situation. I was trying to explain to her how interruptions really held up the flow of my writing and she replied with something like: “Well, we’ll just have to talk to Josh (our son) about how he needs to leave you alone when you’re writing.” It hurt her when I replied that it wasn’t Josh I was worried about, that “she” was the one who most often interrupted me. And no, that isn’t why we’re getting a divorce.