I always have a sentence pop to mind as well! Then I'm like... well... what more do I need to put around it to make it the most enjoyable? What can lead up to this sentence that popped into my head?
Many of my freewrites begin by using the word in a sentence I want to use it in... then just make everything else fall in place, haha :D
If that makes sense? :P
Now I want to know how it continues!