This is great advice. This is my second game jam and planning out my week has made a tremendous difference so far. I'm only a few days in and I'm already starting to have the basis of a fun game. Sure, it looks like crap, but a fun game that looks crappy is still fun. Meanwhile, a crappy game that looks good is still crappy.
My last game jam went pretty well but I was stressing over coding and art at the same time which made things a lot more stressful.