Learning languages or learning science or learning music, etc.
Some people are talented and others are not: that is a fact of life, isn't it?
The science behind it seems to be that some parts of the brain are activated by language, other parts by science and other parts by music etc.
And once a part of our brain is activated, doing what it can do becomes easy.
But before it is activated, it feels very difficult.
I suppose this is an explanation :)