Two more things:
1. Build up as much pressure during your training as you possibly can. Overstrain yourself, do everything extremely hard and fast, and and use the 10-successful-executions-before-you-move-on-method.
2. When playing a match, forget about winning and losing. Focus 100 percent on what you really can control - your next move. There's no score, there's no fumble two points ago, there's just the ball you're playing NOW. Play it as good as you can. Your current possession is the only thing that counts.
Implementing point 2 is very hard because we all want to win. But it's crucial if you want to get into "the zone".
.