From there, it's an easy glide into new writing. You may stop at re-reading, or you might be more inclined to do some revising as well. Mystery writer Jonathan Kellerman likes to begin the day by rewriting and revising the previous day's work, and, as he is doing that, he segues into new material.
Novelists use the technique more often, but poets use it too.
It's the lead-in. I have to rewrite it so many times, so when I re-read it, it looks so awful, sometimes that's discouraging. But it's usually what I've got to do. I've got to read at least the last couple of pages to remember what it is I intend to do next. Going over previous work helps you get back into the same mental state you were in the last time you were in flow.