Guess who was arguably the ultimate journaler in the Bible? David! David wrote most of the psalms, which were the outpouring of the heart of a man who was called "a man after God's own heart." David could have chosen to think or speak his prayers to the Most High, but instead he wrote them! I think he did this for a number of reasons. Could it have been therapeutic to him to write out his prayers to the Lord? Maybe it was to express eloquence through his more poetic psalms. Maybe it was to help him formulate and process what was in his mind and heart in communication to his God.
But David didn't only record His prayer requests to the Lord. He often wrote out God's answers of deliverance, comfort, and strength. He worshipped through the psalms. He confessed and repented. He interceded for his nation. He cried out to the Lord for justice and mercy. He wrote to God and about God.
I think one of the biggest reasons David wrote out his prayers and answers was to have a documented record of what he was saying, being led by the Holy Spirit, for posterity. Look at how who read the Bible have been blessed because of what he wrote.
That's one of the great side effects of journaling God's answers. It blesses us and others. If you're interested keeping an organized, documented record of your time in fellowship with the Father you can find a beautiful wire bound journal here: Remembering His Promises Prayer and Answer Journal
Blessings,
Akiko