For just over fifteen years I had received the Eucharist and sacramental absolution regularly before I myself became a minister of these mysteries. Rarely did I doubt their effectiveness, and if I did it was because of my own poor spiritual disposition and not because I doubted the priesthood.
I don't know if this is normal for a new priest, but sometimes a doubt creeps into my mind when I myself administer the sacraments. Yes, I have always believed in the transubstantiation of the sacrificed bread and wine over which the Great Thanksgiving has been pronounced, but does it "work" when plain old me does it?
This is a good example of how spiritual doubt can help us to notice inadequate theological thinking. For it is not "my" priesthood that makes the sacraments happen, but the priesthood, first of all, of Jesus Christ himself. It is the priesthood of the Church as his Body extended through history. It is the priesthood of the whole people of God, baptized into Christ's eternal identity as Priest, Prophet, and King. It is the priesthood of all the priests who laid hands on me, and of those who did the same for them, all the way back to the Lord's own apostles.
It's only in the smallest sense that it is my priesthood that effects the sacraments at which I preside with God's people. Again, it's like my formation director told me on my ordination day, "it's about the communion of saints. That's the only way this makes sense."