You’re heading toward a place in your story, somewhere you know you’re trying to get to. That might be driving toward an event or getting a character to a particular place or just reaching a zingy image that you want to close a scene with.
Use this exercise to take a detour. Invent an obstacle and insert it into your route so that you’re forced to make a detour. The detour takes a little bit longer to traverse the same basic portion of story sequence, but it also offers new detail, new places to put your attention. The detour introduces you to a locality you might not have otherwise ever thought about or visualized beyond some kind of vague regional idea.
Write the detour. You might want to draw a literal map of the route, populated with points of interest or landscape observations and then write from the map. Then figure out how to rejoin your original route.
You might approach this very literally, as you move a character through space, shunting them onto the wrong train or having their car break down or sending them to do a favor for someone before they can get on with their romance. Or you might think of this landscape through which the detour runs metaphorically: you have been writing a persuasive essay but now you detour into a small anecdote or etymological digression; or you have been writing in one person’s subjective space and you take a detour through someone else’s perception for a while.