Lucky seems to understand that. He growls at my wife or my daughter if they try to enter. Maybe he senses me growling on the inside. I don't like being interrupted. Writing is a kind of self-hypnosis.
Interruptions break the spell, and it's sometimes hard to get back.
I generally write for about two hours a day, the first thing every morning. After two hours I find myself losing energy and concentration. It's best to quit while I'm still excited about the story. Then it will be easier to get started tomorrow. I couldn't write for a longer period, even if I wanted.