Today's Gospel Reading for the Mass was the parable of the sower. Jesus did much of his teaching in parables, perhaps out of a need to simply and elegantly explain complex philosophical issues, or perhaps another reason. For a long time, the parable of the sewer did not make sense to me, beyond a simple analysis.
The "seed", of course, refers to the word of God, but also to various people, much as the "ground" refers to the hearts of people, or their spiritual environment.
Therefore, the seed that falls on the path is a reference, variously, to the Word being wasted on deaf ears, or, more poignantly, to the Word falling upon people who are deeply steeped in the "ways" (ways, roads, paths) of the world. People who believe they are already on a path to salvation or to happiness will not be swayed by verbal witness; for these, the seed will fall emptily. The "birds" which "pluck up the seeds" are the various concerns and vagaries of the world. They are other faiths, they are the temptations to sin, or, most insidiously, the next promotion, the new assignment... whatever pressing concern occupies our minds such that we cannot fully devote time into an examination of self.
The rocky ground speaks of those who are interested, but who cease to learn the Faith soon after learning it. In their enthusiasm, they raise up quick and tall, but when the hardships of life come into play (sun, brightness becomes temptations, heat is opposition) their faith quickly shrivels up.
The thorny ground are those who have a good depth, a good foundation, but is already "sewn in" with other ideas, or surrounded by those with a strong opposition to the faith. These weeds, in whatever form they take, will beat down and choke out uprisings in a person's faith, rending spiritual growth impossible. For a person to grow in spirit, they must clean their spiritual ground of weeds... they must beak up the soil of the packed path so that the seed can go deep, and sift their spiritual garden of rocks.
The people who grow best in faith are the ones willing to set aside all else for God. Am I that person? It depends upon your definition of "all".