A popular metaphor for refactoring is cleaning the kitchen as you cook. In any kitchen in which several complex meals are prepared per day for more than a handful of people, you will typically find that cleaning and reorganizing occur continuously. Someone is responsible for keeping the dishes, the pots, the kitchen itself, the food, the refrigerator all clean and organized from moment to moment. Without this, continuous cooking would soon collapse. In your own household, you can see non-trivial effects from postponing even small amounts of dish refactoring: did you ever try to scrape the muck formed by dried Cocoa Crispies out of a bowl? A missed opportunity for 2 seconds worth of rinsing can become 10 minutes of aggressive scraping.

Source: https://www.versionone.com/agile-101/agile-software-programming-best-practices/refactoring/