The following comes from the Catholic Exchange:
There is nothing so important in the supernatural order as to have a deep, intense interior life. This is so, because at times we run into the error of subordinating the interior life to the practice of the virtues, as if our contact with God were only a means to perfect ourselves.
The case is not thus. There is no doubt that prayer and all the other acts of the interior life have an efficacious influence on the acquisition of the virtues. From our relation with God, we draw the strength wherewith to repel temptations, self-knowledge whereby to be humble, sweetess of temper wherewith to treat with our neighbors, and the light and the strength with which to practice all the other virtues. Even more can be said, for one may be sure that the virtues which do not have their roots in the interior life are neither solid nor deep.
But this does not mean to say that we approach God solely to acquire virtues. On the contrary, the active life and all the virtues we must practice with respect to our neighbor and to ourselves, more than being the reward of our efforts, are the means whereby to achieve the contemplative life, the perfect interior life. In other words, the contemplative life is not a means or a ladder whereby to arrive at the active life. On the contrary, we work, we struggle, we sacrifice ourselves in order to love God, in order to have intimate and loving relations with Him. The true spiritual life consists in our relations with God. Relations with our neighbor and even with ourselves are something secondary; either they are ordinated to achieve the interior life, or they overflow from it.
But the central point of the spiritual life is the contemplative life. Why? Because it is for this that God made us. He made us for Himself, that we might know Him, love Him, and serve Him. Hence, if we sacrifice ourselves to achieve a betterment of our life and conduct, it is solely that we may render ourselves worthy to have communion with God. Thus, our interior life is the summit, the ideal, the goal toward which all our efforts ought to converge.