Do not hover always on the surface of things, nor take up suddenly with mere appearances; but penetrate into the depth of matters, as far as your time and circumstances allow, especially in those things which relate to your own profession. Do not indulge yourselves to judge of things by the first glimpse, or a short and superficial view of them; for this will fill the mind with errors and prejudices, and give it a wrong turn and ill habit of thinking, and make much work for retraction. ~The improvement of the mind, or A supplement to the art of logic. by Isaac Watts
More good advice from Watts:
IX. Once a day, especially in the early years of life
and study, call yourselves to an account what new ideas,
what new proposition or truth you have gained, what
further confirmation of known truths, and what advances
you have made in any part of knowledge; and let no
day if possible pass away without some intellectual gain:
such a course well pursued must certainly advance us in
useful knowledge.
http://catalog.hathitrust.org/Record/009808911
http://hdl.handle.net/2027/uva.x000492799