"There is a Fountain Filled with Blood" was written by William Cowper. The hymn is one of great depth and yet, an all so familiar one, in which we can sing without even thinking about it.
William Cowper struggled with depression and mental anguish from the time of his mother's death at age 6 until the end of his life. He did not come into a saving knowledge of Jesus Christ until he was 33 years old. After his conversion, he lived with a Pastor and his wife. The pastor eventually died, and the widow was invited by Pastor John Newton to move to Olney, England to be part of the fellowship there. Cowper moved as well.
God in his providence introduced Newton to Cowper and Pastor Newton became very instrumental in the day to day goings-on of Cowper and his mental state. He struggled so often with assurance of salvation and depression still. And yet, amazingly, wrote some deep hymns of the faith, that have become landmarks for the Evangelical body of Christ.
He wrestling with doubt. He pushed through the thoughts. He conquered in Jesus' name.
So many times when we as believers go through the valleys that can cause of pain, we feel so alone. We forget those saints that walked before. We sing the hymns and then wonder if we will ever attain to the "sainthood" of the hymn writers. But they are just like us. Wandering sheep seeking the Good Shepherd. He hears our voice and rescues.