On 25 February, 1559 Calvin wrote a little letter in which he
… again spoke of the anxiety and distress which he suffered. The ministers were quarrelling with each other. He exhorted them not to read either the German Theology (La Théologie Germanique), or a little work, entitled ‘Der Neue Mensch”.*
Calvin was a person subject to depression, as had been Zwingli and as had been Luther (to a lesser extent). Depression is the affliction of genius. The price paid for extraordinary intellect. The depression experienced by the Reformers is just more evidence, in case we needed it, of their utter frail humanity.
*P. Henry, The Life and Times of John Calvin, the Great Reformer (Vol. 2).