I used to be terrified of interruptions, when writing, but lately this fear has been diminishing, to the point of me hopping online and chatting and posting quick updates (like this one) without losing my train of thought. It’s all thanks to plotting. I know exactly where I’m going with a scene, and I don’t freak out anymore if I get interrupted. Yes, I get irritated, but I can quickly return to where I was before.
One time at a book fair I saw an author who was typing in between people coming up to his table. I asked him what he was doing. He said he was working on his novel, some number of draft. I was astounded at how he could do it, with the noise and the interruptions. Now I know. I have a plan, and I follow it, and all hell can break loose, but I’ll still write. What a glorious achievement.