"The essence of good cricket is having a clear mind, so the strategy for the fielding side is to get the batsman thinking about other stuff - whether it's the runs he has or hasn't scored in the past, what his feet might be doing, what his head position might be, what the selectors might be thinking about him, what the crowd might be saying," explains Justin Langer, former (excellent IMO) Australia cricket opener.
"As soon as you start thinking about those things, you're away from having clarity in your mind. That's what sledging is for me - sowing some seeds of doubt in a player's mind. But if you're playing well, with that clarity, it can't touch you."
Interesting take on mind power: keep a clear mind when there is around you trying to put you off. This shows great self awareness too: confidence in your own abilities.