An illustration will make our teaching on this subject clearer. Imagine a stream flowing from a spring and dividing itself off into a number of accidental channels. As long as it proceeds so, it will be useless for any purpose of agriculture, the dissipation of its waters making each particular current small and feeble, and therefore slow. But if one were to mass these wandering and widely dispersed rivulets again into one single channel, he would have a full and collected stream for the supplies which life demands.
Just so the human mind (so it seems to me), as long as its current spreads itself in all directions over the pleasures of the sense, has no power that is worth the naming of making its way towards the Real Good; but once call it back and collect it upon itself, so that it may begin to move without scattering and wandering towards the activity which is congenital and natural to it, it will find no obstacle in mounting to higher things, and in grasping realities. We often see water contained in a pipe bursting upwards through this constraining force, which will not let it leak; and this, in spite of its natural gravitation: in the same way, the mind of man, enclosed in the compact channel of an habitual continence, and not having any side issues, will be raised by virtue of its natural powers of motion to an exalted love.
In fact, its Maker ordained that it should always move, and to stop is impossible to it; when therefore it is prevented employing this power upon trifles, it cannot be but that it will speed toward the truth, all improper exits being closed. In the case of many turnings we see travellers can keep to the direct route, when they have learned that the other roads are wrong, and so avoid them; the more they keep out of these wrong directions, the more they will preserve the straight course; in like manner the mind in turning from vanities will recognize the truth.
The great prophets, then, whom we have mentioned seem to teach this lesson, viz. to entangle ourselves with none of the objects of this world's effort; marriage is one of these, or rather it is the primal root of all striving after vanities.
Source: On Virginity (New Advent)