If you're naive like I am, you'll probably believe that you're above distraction. When you're focussed, there's nothing, from your phone ringing to a bomb going off across the street, that can arouse you.
Humans are predatory animals. This makes you very easy to distract because there's a part of your brain that is always turned into the wider environment. Ever see a dog or a cat when they spot something move on the other side of the room? Nothing else matters to them in that moment. I sometimes think that my dog, in that moment, must feel how I do when I hear the notification sound on my phone.
All notifications are not created equal.
Can you remember how many notifications you used to receive before 2007? Just texts and phone calls I'll bet (unless you were one of those blackberry carrying unicorns), but nothing like how it is today. Nowadays, every application on your phone is competing for your attention, and if you have all notifications turned on they have a means to reach out and tap you on the shoulder all day and all night.
I made the decision at the start of 2017 to disable ALL notifications on my phone except for calls and messages. When I'm working I go totally dark and enable "Do not Disturb" mode, which will block all incoming calls and silence all messages except from numbers on your favourites list.
Since I did this a few months ago, none of the discomforting thoughts that were echoing through my mind came back to haunt me. Things like "what if the family dog dies and your mom can't call to tell you" and "people will think you're avoiding them and then hate you", or "you might miss something important". It's comical now but these were some genuine anxieties rattling around my skull before turning off notifications on my iPhone. Welcome to life, millennial.