I heard a presentation from a neuroscientist last week on how our brains work. She highlighted different brain networks that one can imagine working well in some situations (“keep an eye out for tigers and snakes”), but get corrupted into un-, even counter-productive activities in modern circumstances (“keep an eye out for tweets”). We all have these networks and we all live in a world filled with more, and more round-the-clock, stimuli than our ancestors could have ever imagined. Staying on task gets more challenging all the time. Here’s an article from the NY Times Education section that might offer some helpful insights and tips: How to Deal with Digital Distractions (Times, 1 Nov 2016).
You can also test your ability to resist distractions right now: try not clicking on this post from 2013, Like Ketchup on Sushi, that takes you to another Times article, How to Get an A- in Organic Chemistry.