St. Paul calls believers of Thessalonica "imitators of the Lord" who received the Word in "affliction" and "the joy of the Holy Spirit." To imitate is to repeat what another has done. When imitation is made of another out of love, it reveals a beautiful devotion. So one friend imitates the virtues of another because he admires her, and a spouse reveals a deep devotion to her beloved when she attempts to make him feel the love that she has felt from him. Thus, does marriage reveal the Great Mystery.
In the case of the Bridegroom of the Church, He has loved us to the end. He who is Love Himself was hated for our sake. To rescue us from a world dying in its own lies and myths, He suffered the truth of God's love for us and dared to reveal it no matter the cost. With patience, His loving obedience bore away sin until death itself was overcome. How can a believer show his devotion to such a Lover other than to love Him in kind?
This is what St. Paul praises when he singles out believers for receiving the Word in affliction. In welcoming the Word of the Father while they are under trial, they imitate the One whom they love. They suffer the Truth -- for no one can know the Truth until they suffer it in their own life, in the depths of their heart. Only to the degree that we suffer the truth in our hearts do we possess it. Those who believe in the Word suffer this Truth even as they make their way through the work-a-day world as a sign of contradiction - and thus, they too are hated even to the point of sharing in His salvific work.
Holy Spirit, who makes this imitation of Christ possible, gives them joy. The Word connects present afflictions and the Gift of the Holy Spirit. The greater an affliction is born with love filled faith, the more completely the Word is received, and the greater that joy which the Holy Spirit produces in the heart.
He who is the True Life permits us to undergo afflictions only so that we might turn to Him and welcome Him as the Beloved of the Father. As we welcome this Life more deeply into the heart, this Word made flesh speaks with the power of the Holy Spirit and floods our innermost being with unexpected and inexhaustible riches. His Light shines into the most secret depths, and through the power of the Holy Spirit He fills with love abysses that we do not know are there. Indeed, only affliction can open up such depths to these life-giving riches - so did Christ Crucified suffer for us and so does this Risen Lord suffer with us, and so we never suffer alone. Here we find the secret of a joy that the Holy Spirit knows between the Father and the Son - and wherever the Word communicates His riches, the Fire of the Holy Spirit ignites our joy.