I tried learning the MEAN stack last year and the Javascript was just not going in, until someone recommended me Python. I started learning Python and sure enough I've jumped back on the MEAN stack and its become so much more readable for me.
Someone recently said to me, why don't I just focus on one? I said well its because I hop between languages, technologies, one week might be angular js, next might be javascript. It's long but hoping long term I will build up a good collection.
Other thing I find is that i'm quite visual, even though I can do most the logic, I for example with the mean stack, need to draw out architectural plans on paper so e.g I know this files "xyz" and this module should be in example.
Sometimes I find, no matter if you're not getting it or it might be hard, try taking a different approach to it and soon enough you'll grasp it :)