Hard do say, in a passing commentary, I mean.
My first guesses are:
-The reading/listening/watching material you got could be uninteresting/fatiguing and commonplace.
-It might be verbose (long-winded)
-Chances are that you need some minor eye correction aids (glasses, for instance), sometimes people get eyestrain from the computer glare, or even from the artificial lighting (that´s why we see the classification to lamps as warm white/white/cool white.
It´s for nothing that going to the malls the glare is so much that you can´t stay for longer than the time to do the shopping, it´s not by chance that everything moves (the scalators) and the sound, everything screams "move, buy somethig and get the hell out of here"
-It could be that the reading/listening/watching material doesn´t "talk to each other". For example, the Speak Up magazine integrates texts in the ''taped" form and written text, to a learner in the beggining it´s less energy spent. If he/she can´t follow the person talking, can see/read it from the respective written text.
-Other cause is, when the learner get some material that is not on pair with his skills (reading /listening /interpretation skills etc).
-Sometimes is the style of learning, there are people that learn by himself, others need a group to discuss, to practice etc.
And other ways, there are countless possibilities.
Ah, and I hope this doesn´t take longer than five minutes!