When a man is ordained into the priesthood, he is set aside and consecrated for a holy and necessary role in the Church. That role is described succinctly for us by the Augsburg Confession, where it is called the Ministry of teaching the Gospel and administering the Sacraments. One need not be a pastor to be faithful to these essential functions of the Church's ministry. No matter what his title, whether it be pastor, seminary recruiter, campus pastor, military chaplain, hospital chaplain, seminary instructor, headmaster, editor for the publishing house, translator for the publishing house, driver for the synod president, or whatever, a presbyter will be judged according to his faithfulness to the teaching of the Gospel and the administration of the Sacraments.
If you are an ordained priest in the Lutheran Church, and you haven't said Mass for years, or even months, I call upon you, and your confession calls upon you, to remember what the ministry is, and what you are. You are a man to whom God gave a great gift by the laying on of hands. You never lost that gift, by the way. It is still in you. It is a gift "which is in thee" as St. Paul says. He doesn't say, "which was in thee." What you need to do is to stir it up once again. Pray for the gift of the Holy Ghost, that He would renew all His gifts in your life, and that He would renew your commitment to the ministry of the Word of God. He will reorient your life. Ask Him. Ask Him every day, until He both shows you the way, and gives you the courage to take it.
I disagree with the notion that seminary professors ought to be made to serve as parish pastors, for 1. it would be unfair to them and to the people to expect that all presbyters would make good pastors, 2. even if one would be good at being a pastor, it would be unfair to a church to get a pastor for only a short duration, even if it were a year or two, and 3. there are many ways they could keep themselves connected with the ministry of Word and Sacrament. The same goes for the bureaucrats, heads of schools, and whatever else. When you see opportunities to celebrate the Holy Supper, and to preach, take them. When someone asks you to hear his confession, don't go through your mental files of all the reasons why you shouldn't do it. Just do it. You say you are out of practice? I know you are, and hearing confession is the sure way to solve that problem. No one ever asks you? Then you are not writing, teaching, and preaching about it. Not enough anyway.
If you are currently serving in "Word and Sacrament ministry," then I call upon you nonetheless to strive constantly to renew your commitment to it. Ask the Holy Ghost to give you a pure love of the Eucharist. Ask Him to make you a better minister of Christ and of Christ's Church. Ask Him, for He Who can renew the face of the earth can also renew the dry soil in you. He Who brought light to the world by His word can enlighten the darkness in your heart. You don't see any noteworthy darkness in your heart that harms your life of ministry? Have you stopped to think about it lately? Ask God. He will show you.
Christ our Lord, Who gave His life to atone for the sin of the world, wants to give the forgiveness and life that He won for us on the cross to men, women, and children here in the modern world, through your life, work, and witness. His boundless love gushes from His pierced and sacred heart even now. It does so through ministries that are shaped by His cross. Let your ministry bear the marks of the Lord Jesus. If it does, then no man can ultimately trouble you, not even the Old Adam in you.