At the end of the Bespin duel when Luke is cornered, he could look down and back up at Vader... then back down.... and back up over and over again, until finally the disembodied voice of Obi-Wan (taken from ANH) tells him "Let go!"
At the end of the Bespin duel when Luke is cornered, he could look down and back up at Vader... then back down.... and back up over and over again, until finally the disembodied voice of Obi-Wan (taken from ANH) tells him "Let go!"