Hey there. I have to point out that your experience is something that is very common to a lot of people. Retaining a strong focus is actually skill you have to harness. The ideal solution I would like to suggest to you now would be to try meditating. As I have read from http://mindbrain.ucdavis.edu/labs/Saron/lab-news/meditation-helps-increase-at...
the activity really allows you you improve your ability to focus drastically. Try it and let us see how it helps.