Whatever you sow in cultivated ground, you reap the same. If you plant fruit trees, or sow wheat, barley or some other useful crop, the earth brings them forth and they grow and are fruitful. But if the land is left untilled and unsown, it sprouts useless plants, mostly the thorns and thistles mentioned in the curse pronounced against us (Gen. 3:18). Even if a tree happens to grow, it will most probably have no fruit, be useless and full of thorns. It is the same with the soul. Whatever attitudes you instill in it, you receive the same back. If you keep company with good people, listen to spiritual teaching and follow it, putting its precepts into practice, your soul cultivates virtues and becomes useful to God, to others, and to yourself. But if you delight in bad company and do not heed spiritual teaching, or even regard it as trivial, your soul turns wild and out of control, sprouts evil passions, and yields the stings and thorns of its own and the body’s death, namely, sins.
St. Gregory Palamas
"Homily 33: On Virtues and Their Opposite Passions"