We ought to learn the virtues through practicing them, not merely through talking about them, so that by acquiring the habit of them we do no forget what is of benefit to us. ‘The kingdom of God’, as St Paul says, ‘resides not in words but in power’ (1 Corinthians 4:20).
For he who tries to discover things through actual practice will come to understand what gain or loss lies in any activity that he pursues, as St Isaac says; and he can also give advice to others, for he has often suffered and has thereby gained experience.
For some things, St Isaac tells us, appear good, but conceal no small harm; while others appear bad, but contain within themselves the greatest profit.
~St Peter of Damaskos
Prayerful Life 