Yoda falls to the ground, he could of easily jumped back up to Palpatine and continued, the fight was no defeat! Yoda bested Palpatine by deflected Palpatines lightening back at him, over powering him! So then why did Yoda think he lost? They both fell backwards! To end the fight Palpatine should have just bested Yoda in fighting him with a lightsaber, and have Yoda outmatched and then flees from the fight, realizing he's no match for Palpatine!