OF THE ZEALOUS AMENDMENT OF OUR WHOLE LIFE
“Be you watchful and diligent in God’s service and bethink you often why you have renounced the world. Was it not that you might live to God and become a spiritual man? Be zealous, therefore, for thy spiritual profit, for you shall receive shortly the reward of your labours, and neither fear nor sorrow shall come any more into your borders. Now shall you labour a little, and you shall find great rest, yea, everlasting joy. If you shall remain faithful and zealous in labour, doubt not that God shall be faithful and bountiful in rewarding you. It is your duty to have a good hope that you will attain the victory, but you must not fall into security, lest you become slothful or lifted up.
A certain man being in anxiety of mind, continually tossed about between hope and fear, and being on a certain day overwhelmed with grief, cast himself down in prayer before the altar in a church, and meditated within himself, saying, “O, if I but knew that I should still persevere”, and presently heard within him a voice from God, “And if you did know it, what would you do? Do now what you would do then, and you shall be very secure.” And straightway being comforted and strengthened, he committed himself to the will of God and the perturbation of spirit ceased, neither had he a mind any more to search curiously to know what should befall him hereafter, but studied rather to inquire what was the good and acceptable will of God, for the beginning and perfecting of every good work.
Hope in the Lord and be doing good, says the Prophet; dwell in the land and you shall be fed with its riches. One thing there is which holds back many from progress and fervent amendment, even the dread of difficulty or the labour of the conflict. Nevertheless, they advance above all others in virtue who strive manfully to conquer those things which are most grievous and contrary to them, for there a man profits most and merits greater grace, where he most overcomes himself and mortifies himself in spirit. But all men have not the same passions to conquer and to mortify, yet he who is diligent shall attain more profit, although he has stronger passions than another who is more temperate of disposition, but is withal less fervent in the pursuit of virtue.
Two things specially avail unto improvement in holiness, namely firmness to withdraw ourselves from the sin to which by nature we are most inclined, and earnest zeal for that good in which we are most lacking. And strive also very earnestly, to guard against and subdue those faults which displease you most frequently in others. Gather some profit to your soul wherever you are, and wherever you see or hear good examples, stir yourself to follow them, but where you see anything which is blameworthy, take heed that you do not the same; or if at any time you have done it, strive quickly, to amend yourself.”
Thomas a Kempis
The Mark Of God: Understanding Your "I AM Presence" 