First, I think it means that a first cause will never be found. Second, I think it supports the Buddha's statements that searching for answers about the temporal duration of the universe is stupid and a waste of time. Third, and most importantly, these words were spoken so as to induce dispassion, disenchantment, and the abandoning of craving for the five aggregates because there will never be final satisfaction gained from them and all there is in the future is endless rounds of birth, aging, illness and death; it is enough to become disenchanted even with the greatest of pleasures. I think that's the gist of it.
"I don't envision a single thing that, when developed & cultivated, leads to such great benefit as the mind. The mind, when developed & cultivated, leads to great benefit."
"I don't envision a single thing that, when undeveloped & uncultivated, brings about such suffering & stress as the mind. The mind, when undeveloped & uncultivated, brings about suffering & stress."