Jujutsu wasn't that important to the samurai. I wonder why?
Well, sort of, not exactly. Jujutsu as practiced in most ryuha was integral to the core art and was usually a subset of techniques within a sword, spear or other armed art. And it was usually practiced ith a weapon in the obi or in the hand as well.
BJJ'ers: BJJ is judo groundwork, refined and simplified. All body arts share a certain set of principles. The techniques may differ, but the principles remain in effect. Remember, gravity is your friend, and if you can, hit 'em with the biggest thing you can -- the earth.
It also helps to learn a little grappling, so that the mat, as well as gravity, becomes your friend ... or at least friendly territory.