Why don't we have personal robot butlers just yet? The answer is that in order to succeed in robotics, first you have to fail quite hard, and quite a lot.
Speaking at a recent Maker Faire in the US, RoboGames founder David Caulkins noted:
The one thing for anyone in this room that wants to become a roboticist: You have to get very, very, very good about accepting failure. Because building a robot, no matter what kind of robot it is, whether it’s a wheeled robot, remote-controlled robot, a walking robot, an artificial intelligence robot, you’re going to fail a lot. So the people who become good roboticists are the people who can accept that and move on and fix it, and fix it again, and fix it again.
Or in other words, persistence and iteration leads to success. I'm sure I've heard that somewhere else before.