Vanilla is a product of Lussumo:
Documentation and Support.
Personally I just fall into a zone. Some days I can write for hours on end and the words just come to me, and I never leave my computer. Other days I have a hard time just stringing a coherent sentence together.
When you feel it, just do it.
I learned when I'm not writing, but still want to work on my project, I do research to fill the time until something clicks.