Is it not haughty to be as certain as you are? You have to be modest, right?

Luther:

On the contrary, a Christian rejoices in certainty! Surely it is miserable if you are always just insecure? Of course, I also know that it is stupid to be haughty about side issues. It is even sin. But when it is about the heart and the essence, about Christ, nothing is so normal among Christians as making firm statements. When you abandon that, you abandon the Christian faith itself. The Holy Spirit is not a doubter. He does not place unclear presumptions in our hearts, but firm convinctions, more sure and more firm than life itself and than everything you experience.