I’ve seen problems where folks were trying valiantly to move forward with the wrong abstraction, but having very little success. Adding new features was incredibly hard, and each success further complicated the code, which made adding the next feature even harder. When they altered their point of view from “I must preserve our investment in this code” to “This code made sense for a while, but perhaps we’ve learned all we can from it,” and gave themselves permission to re-think their abstractions in light of current requirements, everything got easier. Once they inlined the code, the path forward became obvious, and adding new features become faster and easier.The moral of this story? Don’t get trapped by the sunk cost fallacy. If you find yourself passing parameters and adding conditional paths through shared code, the abstraction is incorrect. It may have been right to begin with, but that day has passed

Source: The Wrong Abstraction — Sandi Metz