Three main paths of mental activity need to be exercised: In, within, and out.
In: Read and listen, accept everything Nature has to offer.
Within: Having taken-in information, convert it into knowledge and wisdom by bathing it in the light of Reality. Digest your mental food in the stomach of the Earth.
Out: Speak and write, so other parts of your mind (which includes other people) can benefit from your gain.
These three pathways are intimately linked: if you wish to function fully you must develop all three to their capacity. Therefore, when you read, do not merely read, but think, and write, and sometimes read aloud, ensuring the development of a balanced mind.