Theologically, this tension or contrast is often described in terms of sin and forgiveness or grace, or in the training I received, "Law and Gospel." In short, we are sinners, unable to save ourselves. God in His mercy freely saves us for Jesus' sake (the cross). Pastors are called on to preach sin and salvation in Christ.
Generally speaking, who can criticise a principle such as this? It seems simple, clear and straight forward enough. I am the sinner and Jesus is the Savior. All of Christianity embraces this truth in one degree or another. There is certainly not anything unbiblical about these basic teachings.
What then is the difficulty? Laetare is probably as good an example as any. "Laetare" means rejoice. In this age of de-pression, austerity, etc., one is almost made to feel guilty for reading or hearing the psalmist say, "I rejoiced at the things that were said to me: we shall go into the house of the Lord." We know there are many forces at work here. Even those of us who go into the house of the Lord do not always do so with gladness. Still, we ought not feel guilty or be made to feel guilty if attending church brings us spiritual benefit. With all of the emphasis on sin I hear lately, maybe it's a good thing that Laetare sneaks into Lent as Gaudete had done with Advent.
We get the point - Jesus is the Savior from sin. This is no small thing. The Cross is no small event. But neither is the Incarnation. Here is where the Creed is helpful. The Creed does not pit the Cross and the Incarnation against each other as I have often heard discussed in recent years. The Creed confesses all of the merciful and saving works of God in Christ from the Incarnation to the Ascension. All of what Christ does for us is central to the work of our salvation. The Creed helps saves us from ourselves and our own notions.
Back to Law / Gospel. There is no way any paradigm can be forced onto a given text. For example, in the healing of the blind man (John 9) the blind man says, "Now we know that God does not hear sinners; but if anyone is a worshiper of God and does His will, He hears him." We can relate to the first part about being sinners, no problem there. What about the second part, isn't the blind man commending doing good things to ensure God's hearing? If we look at the text via a principle the blind man is certainly advancing a theological error. On the other hand, if God can heal a blind man and create faith through hearing of the Word, certainly He can lead sinners to worship Him and do His will, albeit imperfectly. So we hear the blind man charged with being "completely born in sins" and cast out. What does Jesus have to say about this? He finds the blind man and asks him, "Do you believe in the Son of God?" How does it all turn out in the end? The blind man says, "Lord, I believe!" The Evangelist records, "And he worshiped Him."
A couple of observations, not every text is going to say to me that I am a sinner and Jesus is my Savior. Nor is it always easy for the preacher to make that connection with every text or put a principle onto a text. The text also shows us other things about God and man that are not always necessarily interior or based in angst and anfechtung. For example, Jesus is more concerned that the once blind man (and we) "believe in the Son of God." The man now seeing, sees a man externally and sees Him as the Son of God and worships Him. There are both external and internal aspects of the faith. This is indeed what we confess in the Creed, "I believe . . . all things visible and invisible . . . and in one Lord Jesus Christ . . . God of God, Light of Light . . ."
A final observation - in an age of de-pression and austerity, when sin and law are overemphasized, it is better to see things like the blind man did. Then Laetare is not as difficult a thing as it may first appear. Lent may seem to be a more somber time. There is some truth to that. Still, the Scripture for our hearing is here as it is throughout the year, and sometimes it manifests itself more richly, or He manifests Himself more clearly, to us than we may at first expect. If Lent is all about our feelings, then there is no reason to receive the gifts of God. Rather Lent is all about the one of whom the once blind man said, "If this Man were not from God, He could do nothing."