When you don’t do something to write instead, but don’t start writing until you would be done writing:
Everyone died because she was late. The sun rose and time spun out of control; the fiery rays, as they breached the horizon, scorched the city. Its inferno left behind only overcooked corpses. All except her. Because she had miscalculated. Because she become distracted.
If she had known it was all going to be destroyed anyway she might as well have done what she enjoyed. That little amusement she had wanted. If she was going to get here as if she had done it, rather than stopping to make sure she was on time, what was the point of bothering with anything?
Stomping on the still burning embers, she scooped up the smoldering clay. She would burn everything instead. What else was there to do?