What goes wrong when you ignore that defaults can be designed?

The most common reason fails: Trying to redesign all your defaults at once. Default design requires cognitive resources for the transition period — until the new behavior becomes automatic, you are spending willpower maintaining it. Redesigning three defaults simultaneously depletes the budget that any single redesign needs to succeed. Start with one. Let it stabilize. Then move to the next.

The fix: Choose one default you identified in L-1062. Write three columns on a page: Environment, History, and Friction. Under each column, write every factor that currently sustains the old default. Then, for each factor, write one specific change you could make this week to redirect that driver toward a new default. Implement all changes simultaneously and observe what happens for fourteen days, noting which drivers were most powerful and which redesigns held.

The underlying principle is straightforward: You can deliberately choose what your default behaviors are.