Charles Spurgeon was one of the greatest preachers the world has ever known (1834-1892). He preached at the Metropolitan Tabernacle to thousands. His sermon preparation was unique. Late Saturday evening, he would often go into his study and jot down a few notes for his sermon on Sunday morning. Sometimes they were but a few lines. At other times, they were more extensive, but rarely more than a page. What came out of his mouth was pure gold. I encourage you to read any of his thousands of published sermons to see what I mean.
I am quite the opposite of Spurgeon. I rarely preach on Sunday without a full manuscript of what I intend to say, having prepared for days. But, things changed for me this past Sunday. Due to various events that took place in our worship service, I ditched my prepared sermon and preached a sermon that I prepared in the pew as the service was going on.