Brian Tracy opens with the book's titular metaphor: tackling your most difficult, most important task ('eating the frog') first thing, before any other work, prevents procrastination and builds momentum for the rest of the day.

Why tackling the hardest task first works:

• Difficult, important tasks are the ones most likely to be procrastinated on if not addressed immediately, since easier tasks provide more comfortable alternatives
• Completing the hardest task first provides genuine momentum and a sense of accomplishment that improves the rest of the day's productivity
• Delaying the hardest task, even while completing other work, often creates ongoing background anxiety about the undone difficult task

This opening establishes the book's central, memorable metaphor and practical instruction, providing the foundation for its subsequent related productivity principles.