This is my rough calculation, based on about six years of writing full-time.
Every little interruption, be it checking your email, or Twitter, or answering the phone, or the door, or talking to someone in person, kicks you out of the concentrated writing mode, and it will take you 30-40 minutes to get back into it.
So if you only have 1 hour to write, or even less, a single interruption can cripple your whole writing day.
Hide.
Hide well.
Create a hide-out that is free of interruptions you can foresee, and those you can’t foresee. Sometimes they’re sneaky and elusive.
For example, for months I was tolerating notifications on my phone even when it was turned on silent, until one day I simply turned them all off and set my phone to airplane mode every time I write. Why didn’t I do it before?
Another example. I switched from answering emails once per day to once per week, on Monday nights. Answering emails was the major irritant as well as the most dreaded daily task. And it could drop on my head at any time. Now I've created an auto-response that directs folks to my Patreon, where they can become Hamsters and message me on Discord, which I check every day (and love checking it! as opposed to checking email).
Another example. I have batched all my writing tasks. On Mondays I now pre-write and schedule Patreon and blog posts for a whole week ahead, and then on Tuesday, Wednesday, and Thursday I can simply write without worrying about posting/blogging/whatever. I’ve also freed up Friday and Saturday for family (used to never have time) and Sunday for me, TO DO NOTHING (yes, you read that right). It has created more concentrated writing time for me as ever before.
What’s your example/examples?
How do you deal with interruptions?