It was recommended to us that we use a method called practice practicing. Basically what this means is I give DS something to do, tell him it's just practice and in the trash it goes when he's done. We check the answers and occasionally say "oh look, you misses one" and in the trash it goes.
Sounds kind of odd, but it has worked really well for us. The second thing is to play games of chance where winning and losing are completely random. This teaches them that not everything in life has to be or can be controlled.
