Imitation of Christ: Book 1, Chapter 13 Of Resisting Temptations
As long as we live in this world, we cannot be without temptations and tribulations. Hence it is written in Job "Man's life on earth is a temptation." Everyone therefore should be solicitous about his temptations and watch in prayer lest the devil find an opportunity to catch him: who never sleeps, but goes about, seeking whom he can devour. No one is so perfect and holy as sometimes not to have temptations and we can never be wholly free from them. Nevertheless, temptations are very profitable to man, troublesome and grievous though they may be, for in them, a man is humbled, purified and instructed. All the Saints passed through many tribulations and temptations and were purified by them. And they that could not support temptations, became reprobate, and fell away.
Many seek to flee temptations, and fall worse into them. We cannot conquer by flight alone, but by patience and true humility we become stronger than all our enemies. He who only declines them outwardly, and does not pluck out their root, will profit little; nay, temptations will sooner return and he will find himself in a worse condition. By degrees and by patience you will, by God's grace, better overcome them than by harshness and your own importunity. Take council the oftener in temptation, and do not deal harshly with one who is tempted; but pour in consolation, as thou wouldst wish to be done unto yourself. Inconstancy of mind and little confidence in God, is the beginning of all temptations. For as a ship without a helm is driven to and fro by the waves, so the man who neglects and gives up his resolutions is tempted in many ways.