It’s good to flex those creative muscles.  This is similar to improvisation at the piano.  Just sit and write the first thing that pops into your head before diving into that WIP!  Gertrude Stein called this “automatic writing” and it is.  It’s freedom, often unfocused, and really helps one to get in the zone.
Here’s my free write for today.  I will be working on finishing that draft of The Runaway Train as soon as this is posted.

Tiny flashes of light blink between the trees. The woods are filled with dancing fireflies. A gentle mist has risen just above the grass, making the allure of mystery all the more enticing to a young lad armed with a Mason jar and curiosity.
What was lost cannot ever be found, the annals of time have giant maws.