Andrew Pettegree said this quote

In Martin Luther's life and behavior is very courteous and friendly, and there is nothing of the stern stoic or grumpy fellow about him. He can adjust to all occasions. In social gathering he is gay, witty, ever full of joy, always has a bright and happy face, no matter how seriously his adversaries threatening him. One can see that God's strength is within him. – Petrus Mosellanus