As an explanation of the title, the author writes:
Mark Twain once said that if the first thing you do each morning is to eat a live frog, you can go through the day with the satisfaction of knowing that that is probably the worst thing that is going to happen to you all day long.
I could not find the source for this quotation. It appears in various forms on motivational websites, in collections of quotes, etc., but never with any bibliographical details. Project Gutenberg’s collected works of Mark Twain include references to frogs, but nothing that I could see about eating them.