@taamvan:
The best players of chess play it like poker; your opponents know your preferences and predilections and it is your job to lure them into the trap of assuming you will act in the same was as before, or the same way the last grandmaster did, or the same way they would.
One of the best anecdotes I’ve ever heard about psyching-out an opponent at chess is the story of a tournament (I forget which grandmasters it involved) for which Player X had, among other things, carefully prepared for the possibility (indeed, the probability) that Player Y was going to use Opening Z, which Player Y was known to be fond of. In game after game during the tournament, Player Y – contrary to expectations – kept using openings other than Opening Z. Player X eventually became so frustrated that he ended up using Opening Z himself.