"But when we get into the all or nothing knock-out phase ... There's a shift from being motivated by desire to [being] motivated by a fear of failure. When that happens they get tense and the players' skill level drops off."
Dr Hermansson has worked with the New Zealand teams which went to the last three Olympic Games.
He said the team needed to block out the pressure, develop an awareness of their thinking during matches and focus on their performance.
"The athletes which succeed are the ones which are able to manage the pressure and keep the importance of the outcome separate from how they perform."
New Zealanders tended to put more pressure on their athletes than other countries because sport was such a huge part of the national identity, he said.
"We're a small nation and on the world stage, we're pitched as underdogs who'll beat anybody.
"There's a whole dilemma about being a small nation punching above our weight and the situation where the expectation goes up and we're unable to manage that."
In larger countries there were numerous other sports teams to turn to if their rugby team had a loss, but in New Zealand everything came down to rugby and the All Blacks.
He said New Zealanders needed to change their expectations of the All Blacks which would help the team go further in the tournament than they had in recent World Cups.
But the sports psychologist said that this time round would be "ultimately better" - particularly given their recent losses, such as last weekend's Bledisloe Cup match against Australia.
"Expectations have been adjusted a little bit which should enable the team to be able to keep their focus much more on the need to perform well, rather than the focus on the expectation to win."
He said competing on homeground also boded well because the team would be closer to their loyal support base.
"And the other reason is that there's a lot of players in the team's core that experienced the loss at the World Cup four years ago and they have a realisation that it's terrible if we don't win it, but it's not the end of the world."
HOW NOT TO CHOKE
* Block out the pressure
* Concentrate on the performance
* Focus on each match as it comes