3 But when it became our duty to pursue the blessed life of monks, and the true philosophy, our balance was no longer even, but his scale mounted high, while I, still entangled in the lusts of this world, dragged mine down and kept it low, weighting it with those fancies in which youths are apt to indulge. For the future our friendship indeed remained as firm as it was before, but our intercourse was interrupted; for it was impossible for persons who were not interested about the same things to spend much time together. But as soon as I also began to emerge a little from the flood of worldliness, he received me with open arms; yet not even thus could we maintain our former equality: for having got the start of me in time, and having displayed great earnestness, he rose again above my level, and soared to a great height.
Source: On the Priesthood (New Advent)