The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
"My Son, thou art never secure in this life, but thy spiritual armour will always be needful for thee as long as thou livest. Thou dwellest among foes, and art attacked on the right hand and on the left. If therefore thou use not on all sides the shield of patience, thou wilt not remain long unwounded. Above all, if thou keep not thy heart fixed upon Me with steadfast purpose to bear all things for My sake, thou shalt not be able to bear the fierceness of the attack, nor to attain to the victory of the blessed. Therefore must thou struggle bravely all thy life through, and put forth a strong hand against those things which oppose thee. For to him that overcometh is the hidden manna given,(1) but great misery is reserved for the slothful.
2. "If thou seek rest in this life, how then wilt thou attain unto the rest which is eternal? Set not thyself to attain much rest, but much patience. Seek the true peace, not in earth but in heaven, not in man nor in any created thing, but in God alone. For the love of God thou must willingly undergo all things, whether labours or sorrows, temptations, vexations, anxieties, necessities, infirmities, injuries, gainsayings, rebukes, humiliations, confusions, corrections, despisings; these things help unto virtue, these things prove the scholar of Christ; these things fashion the heavenly crown. I will give thee an eternal reward for short labour, and infinite glory for transient shame.
3. "Thinkest thou that thou shalt always have spiritual consolations at thy will? My Saints had never such, but instead thereof manifold griefs, and divers temptations, and heavy desolations. But patiently they bore themselves in all, and trusted in God more than in themselves, knowing that the sufferings of this present time are not worthy to be compared with the glory which shall be revealed in us.(2) Wouldst thou have that immediately which many have hardly attained unto after many tears and hard labours? Wait for the Lord, quit thyself like a man and be strong; be not faint-hearted, nor go aside from Me, but constantly devote thy body and soul to the glory of God. I will reward thee plenteously, I will be with thee in trouble."(3)
(1) Revelation ii. 17. (2) Romans viii. 17. (3) Psalm xci. 15.