Remember past knowledge and improve concentration

Hello Dhananjay,

This morning I reread a religious scripture I have not been reading for the past 10 years.
What strikes me is that yesterday I could not remember any details of it, yet today when I start to read it, I immediately recall the content of the next paragraphs.

This implies that the knowledge obtained in the past was not lost, but stored somewhere in the brain, however seems a human being can't hold access to it... he "forgets" it.

It reminds me of the following quote about Swami Vivekananda's life: "Once Swami Vivekananda was reading the volumes of 'Encyclopedia Britannica'. His disciple associate (Sharatchandra Chakravarti), seeing those twenty-four volumes, remarked, "It is difficult to master the contents of so many volumes in one life." He did not know at the time that the Swami had already finished ten volumes and was reading the eleventh. "What do you mean?" said Swamiji. "Ask me whatever you like from those ten volumes and I can tell you all about it." The disciple, out of curiosity, brought down the books and asked Swamiji many questions on difficult and varied topics/subjects, selecting one or two from different volumes. Swami Vivekananda not only replied each correctly, but in many instances he quoted the very language of the books!"

My question if two-fold:

1.
How can a human being remember all past knowledge? Is it by the practice of brahmacharya, or specific meditation techniques?

2.  
Swami Vivekananda said that concentration is the essence of knowledge; nothing can be done without it, and that 90% of thought force is wasted by the human being.
How can concentration of the mind be improved and become very strong, so that little thought force is wasted?

Pulong

Namo Amito Fo
Namo Amito Fo