If there were no insecurity, we would not know of security. If there were no blindness, we would not be conscious of perception. If there were no poverty, we would not experience riches. If no man ever imposed restraint on others, there would be no striving for liberty and the term would not exist. Gravitation, for instance, is a physical force drawing all and sundry toward the earth's center.
Obstacles are assuredly the source of aspirations.
This encompasses an enormous realm, including every thought that reveals truth - repeating it over and over again, seeking improvement. True glory consists in writing what deserves to be read - There are countless thousands of books, articles and commentaries that deserve to be read. The vast majority of these writings are known to a mere handful of people. You Are Extraordinary by Roger J. Williams. This led the Professor to his first study in human variation, having to do only with the variation in taste buds in different people.