Why the Pursuit of Things is and Empty End: 'The Imitation of Christ'

3. The Beloved: My son, a man often goes in eager pursuit of something he wants; when he has got it, he doesn't feel the same about it. Man's affections are unstable, and are apt to drive him from one desirable object to the next, so that even in trivial matters it is well worth renouncing oneself.

4. For a man to make real spiritual progress, he must deny himself; a man who has made this renunciation enjoys great freedom and security . . .

~ Thomas á Kempis, The Imitation of Christ (Knox translation), From Book 3, Section 39