Obviously it is best to arrange things so that you can have some private time to yourself. I suggest you turn your phone off or just ignore it and don’t answer it.
You can let people in your home know that you don’t want to be disturbed for twenty minutes or so. In some cases you could choose just not answer them if they interrupt you and hope they go away! But of course they may not always be that considerate!!
And obviously if it is urgent, you would just open your eyes and deal with the situation. Probably better to take the option of going back to the beginning and starting again afterwards. It might depend on how long your interruption was.
At most it would be like having someone disturb you when you were dozing. There can be no possible harm from being interrupted.