There are all sorts of things that contribute to the formation of a pastor, but Confession and Absolution is surely one of the most significant.
It is the Divine Call and Ordination that actually put a man into the Office of the Holy Ministry and make him a pastor. In that, he is under orders to preach the Gospel, to teach the Word of God, to catechize and care for the sheep allotted to his care, to hear confession of sins and absolve the penitent in the Name of Jesus. The Lord provides the necessary gifts for the fulfilling of this Office, even as He also provides the pastors themselves with which He fills it.
Christ and His Spirit are the substance of the Office and the sole sufficiency of each pastor within the Office. Yet, the Lord provides His ministers with a variety of native talents and abilities, and He prepares them for His service by the agency of those whom He has previously raised up for the teaching of His Word and the pastoral care of His Church on earth. A man who will become a pastor in the Church, first learns what that will mean from the practice and care of his own pastors. He will learn additional knowledge and grow in understanding through the instruction of his professors (however such instruction may be ordered and arranged by the Church). He will learn even more by the trial and error of experience. There is no shortcutting nor substitute for the wisdom that is gained by the actual preaching and administration of the Gospel.
More and more I am convinced that the confessional may be the most profound context within which a pastor learns to be what he is called and ordained to be. Confession and Absolution remains one of the most humbling experiences for me (no matter which side of the confession I may be on); it is also one of the most instructive. There is no cookie-cutter approach to this practice. One learns by doing it. Here, more than anywhere else, the proper distinction of the Law and the Gospel is most tangible and practical and downright urgent. The discipline of self-examination and confession teaches the Law more pointedly and personally than any textbook. The speaking of Absolution to a penitent, the forgiving of that sinner in the Name of Jesus, teaches the Gospel more profoundly and compellingly than any lecture. The best and most helpful textbooks and lectures will have been written by those who have spent time in the confessional.
Preaching the Gospel is not exactly the same thing as Absolution, but it is one and the same Gospel that is proclaimed in each case. The best preachers of the Gospel are those who regularly hear confession and forgive the sins of those who repent. They may not be the most eloquent or artful, but they will be the most pastoral, and they will speak to the heart of the matter; because they have learned how to speak to the heart of Jerusalem that her warfare is ended, her iniquity pardoned.
There are other ways in which pastoral care is given, but the purpose of genuine pastoral care is always repentance and faith in the forgiveness of sins. Thus, Confession and Absolution stands at the heart and center of pastoral care; because the Office of the Holy Ministry is defined by the Office of the Keys. Apart from the regular practice of Confession and Absolution, pastoral care is inclined to warp into "counseling," which is more than likely to put the Law (or a law of sorts) in the central height that belongs by right only to the Gospel.
Certainly, catechesis happens elsewhere than in the confessional. I'm increasingly convinced that everything is finally a form of catechesis (whether good, bad, or otherwise). But the best and most faithful catechesis will lead to and from the confessional, as surely as it leads from the font to the altar, and to and from the altar back and forth within one's vocations in life. Proper Christian catechesis is the way and means of returning disciples to Holy Baptism through the Law that kills the sinner and the Gospel that resurrects the sinner with Christ Jesus in faith. Confession and Absolution is the pinnacle of such catechesis.
Frankly, hearing confession is no more fun than going to confession; yet, we ought to find comfort and satisfaction in sharing this means of grace in the fellowship of the Body of Christ. I know that my Christian faith and life are tremendously served and strengthened by going to confession and receiving Absolution from my own pastor. In this I greatly rejoice, even if the process is momentarily painful and unpleasant; it shatters my prideful old Adam, that Christ may be raised in me.
As a pastor, not only do I learn to know and name my own sin for what it is, in order to seek the forgiveness that comes only from Christ by His Word and Holy Spirit; I also learn to understand, from the inside-out, the very sort of hurts and fears and suffering and shame to which I am sent with the healing medicine of the Gospel for the people of God. And in absolving individual penitents who have opened themselves up to me as the physician of their souls, I am also cured of the proclivity to speak the Gospel generically and abstractly.
I have learned to be a better pastor in the confessional, and that is for the good of the Gospel. It has also been my experience and observation that, among my colleagues near and far, those that regularly practice Confession and Absolution are better preachers, better catechists, and better able to speak the Word of the Lord in any conversation, any context, under any conditions. They say what needs to be said with clarity and straightforwardness, but also with the sort of charity and compassion that can't be fabricated by any pretense.
The real love of the Gospel doesn't dance around the difficult subject or avoid the awkward elephant in the room; it goes to the heart with the truth, both the Law that kills and the Gospel that gives life. That is what each and every pastor is given to do all the time, but it comes more readily and often with the practice of Confession and Absolution. Which is why I still agree and fervently maintain that the Office of the Keys is the key to the renewal of the Church.