Let's quote some Luther

"You know the real basis and foundation of your salvation, on which you must rest your confidence in this and all troubles, namely Jesus Christ, the cornerstone, who will never waver or fail us, nor allow us to sink and perish, for he is the Saviour and he is called the Saviour of all poor sinners, of all who face tribulation and death, of all who rely on him and call on his name."

In Theodore Tappert(ed) Luther: Letters of Spiritual Counsel (Vancouver, British Columbia: Regent College Publishing, 1995)