When Darth Vader first met Luke Skywalker at Lando's Super Carbonite Rave Party, he was shocked to see what a noob his little bastard child had turned out to be. Not only in the glorious ways of the Sith, but also in other matters. (Luke had tried to make it with his sister once). So Vader had a little talk with him about the birds and the Wookiees, which is where the above line comes from. Luke refused to listen so Vader took a more direct approach and cut off his hand. Luke got a super-cool robot hand, which made his nightly routine more efficient and pleasurable.