The power of the negative

So, Rugby fans; What about the British and Irish Lions and their performance on Saturday in the second test against South Africa? What could have (should have?) been... A moment of madness from an experienced International (O'Gara) cost the match and the series. Like a moth to a flame, he couldn't seem to avoid doing the one thing that he shouldn't do - concede a penalty. Simon Barnes, writing in the Times summed it up really well - "I bet every time O'Gara walks past a Wet Paint sign he ends up with coloured hands".
Then, last night, when Murray seemed to be on the up in the fourth, ahead by 2 sets to 1, he double-faulted a couple of times and played some very sub-standard shots that allowed Wawrinka to take him to five sets.
It's a common theme in communication/delegation/influencing workshops - "Tell people what you want them to do and not what NOT to do". The negative 'I mustn't do this...' becomes such a focus for the individual, especially under pressure, they can't help but do the one thing they know is their downfall. Even the professionals fall foul of this phenomenon - so next time you give an instruction, ask yourself - am I setting up that person to succumb to the 'power of the negative'?