Thomas a Kempis, The Imitation of Christ 3.12

Of the inward growth of patience, and of the struggle against evil desires

1. O Lord God, I see that patience is very necessary unto me; for many things in this life fall out contrary. For howsoever I may have contrived for my peace, my life cannot go on without strife and trouble.

2. "You speak truly, My Son. For I will not that you seek such a peace as is without trials, and know no adversities; but rather that you should judge yourself to have found peace, when you are tried with manifold tribulations, and proved by many adversities. If you shall say that you are not able to bear much, how then will you sustain the fire hereafter? Of two evils we should always choose the less. Therefore, that you may escape eternal torments hereafter, strive on God's behalf to endure present evils bravely. Think you that the children of this world suffer nothing, or but little? You will not find it so, even though you find out the most prosperous.

3. "'But,' you will say, 'they have many delights, and they follow their own wills, and thus they bear lightly their tribulations.'

4. "Be it so, grant that they have what they list; but how long, think you, will it last? Behold, like the smoke those who are rich in this world will pass away, and no record shall remain of their past joys. Yes, even while they yet live, they rest not without bitterness and weariness and fear. For from the very same thing wherein they find delight, thence they oftentimes have the punishment of sorrow. Justly it befalls them, that because out of measure they seek out and pursue pleasures, they enjoy them not without confusion and bitterness. Oh how short, how false, how inordinate and wicked are all these pleasures! Yet because of their sottishness and blindness men do not understand; but like brute beasts, for the sake of a little pleasure of this corruptible life, they incur death of the soul.You  therefore, my son, go not after your lusts, but refrain yourself from your appetites. Delight you in the Lord, and He shall give you your heart's desire.

5. "For if you will truly find delight, and be abundantly comforted of Me, behold in the contempt of all worldly things and in the avoidance of all worthless pleasures shall be your blessing, and fullness of consolation shall be given you. And the more you withdraw yourself from all solace of creatures, the more sweet and powerful consolations shall you find. But at the first you shall not attain to them, without some sorrow and hard striving. Long-accustomed habit will oppose, but it shall be overcome by better habit. The flesh will murmur again and again, but will be restrained by fervor of spirit. The old serpent will urge and embitter you, but will be put to flight by prayer; moreover, by useful labor his entrance will be greatly obstructed."