It is very difficult to keep focus now that we have such an information overload. Everywhere you look someone is trying to feed information into your brain. I believe that if you can stay calm and know what is currently important , take deep breaths and focus you will gradually train your brain to think this way.
Even now, I have many tabs open and before even finishing this post, I wanna click on one of them and see the latest updates. You need to compartmentalize what you are doing and not let anything in until you complete your task.
It is difficult but very possible, just gotta keep trying.