Robert Robinson was a wild young man who came to repentance listening to a George Whitefield sermon. He later became a pastor and wrote a couple of hymns, particularly the famous, "Come Thou Fount of Every Blessing", which was written in 1757.
Later in life, Robinson wandered from the Lord and apparently felt he could not return. Perhaps as the the story of Pilgrim's Progress, when Christian and Hopeful were captured by Giant Despair and taken to Doubting Castle, he too fell prey to the devil's lies and forgot for a time the Promises of God. For those who aren't familiar with Pilgrim's Progress, Christian and Hopeful escape Doubting Castle when Christian realizes he has a key called Promise, which will open all the doors and gates of Doubting Castle.
It is said that Robert Robinson also found that he had a key called "Promise" when years later, he was riding in a stage coach with a young woman who did not know who he was but actually quoted the hymn, Come Thou Fount, to him. He replied, "Madam, I am the poor, unhappy man who wrote that old hymn many years ago, and I would give a thousand worlds, if I had them, to enjoy the feelings I had back then."
It is said that she responded by telling him “Sir, the ‘streams of mercy’ are still flowing.”