This excerpt of St. Thomas is taken from Saint Thomas Aquinas: Meditations for Every Day, compiled and translated by Rev. E.C. McEniry, O.P., from selections of St. Thomas' writings, especially the Summa Theologica.
"We glory in tribulations, knowing that tribulation worketh patience, and patience trial, and trial hope. And hope confoundeth not, because the charity of God is poured forth in our hearts" (Rom. 5,3). Here St. Paul tells us of the advantages of sorrows and the power of hope by which we expect to win the prize of eternal glory and become the children of God. When we earnestly desire something, we freely endure whatever is difficult and disagreeable to obtain our heart's desire; just as a sick man, if he anxiously desires health, willingly drinks the bitter medicine so that he might be cured by it. Therefore a sign of the earnestness of our hope, which we have because of Christ, is revealed by us when we not only rejoice in the hope of everlasting glory, but also when we patiently endure evil things for the possession of that glory. Hence it is said: "We glory in tribulations," through which we may win the crown of deathless fame. "Through many tribulations we must enter the kingdom of God" (Acts 15, 21). And St. James (1,2) writes to the faithful: "Count it all joy when you fall into different temptations."
"Tribulation worketh patience," not that tribulation is the effective cause of patience, but that tribulation and trials and sorrows of every kind are the occasion and material of performing an act of patience.
"Patience worketh trial." Therefore, it is written in Ecclesiasticus (2,5), "Gold and silver are tried in the fire, but acceptable men in the furnace of humiliation. Take all that shall be brought upon thee, and in thy sorrow endure, and in thy humiliation keep patience." We endure easily the loss of a person of thing if we love God and eternal things more than the loss which we have sustained. Hence, if anyone patiently endures corporal and temporal sufferings for the sake of possessing eternal happiness, it is sufficiently clear that such a person loves the eternal good things more than temporal treasures from which death separates us all.
"Trial worketh hope," for tribulation prepares the way for hope. Hence, if anyone earnestly rejoices in eternal hope, it follows that he must glory in tribulations from which there is no escape in this life.
"Hope confoundeth not," that is, hope does not abandon its object. Man falls into despair and loses hope, only when he fails to pursue the eternal Object of all his hopes, desires, and natural aspirations.
"The charity of God is poured forth in our hearts." The charity of God can be twofold, namely the charity with which God loves us, and the charity with which we love God. When we love Him, it is a sign that He loves us. Now the love of God for us is oft-times shown to us in the sorrows, tribulations and trials which enter our lives, our homes and our fortunes. Consequently we all need charity and prudence and patience, in order that we might turn to our advantages the crushing afflictions, deep rooted sorrows and heavy burdens of every day life.