In the wide-ranging interview with All Blacks TV, Hansen reflected on the All Blacks' Rugby World Cup 19-7 semifinal loss to England.
Hansen concedes that the match still hurts and he has had a lot of time to reflect on it.
"It's still one of those things that bugs you, it still hurts and will do for the rest of time," he said.
"Why did we lose the World Cup? Well, we lost to England, and why did we lose to England? I've reflected on that quite a lot."
Hansen went on to explain that the massive win over Ireland did them no favours, as they may have relaxed a little bit ahead of a task that no side has achieved, winning three World Cups in a row.
"What we were trying to do has never been done before, and with success comes a little less desperation.
"It was a perfect storm really, we played South Africa first up, got that job done, had lesser opponents after that so that mental side of the game didn't come into it.
"We had a massive week into [the quarterfinal with] Ireland, and that was a game that had everyone on the end of their seat. When we won that and won it so comfortably, subconsciously I think all of us may have relaxed a little bit. Let go of two percent of that desperation we had. It's not something that you do deliberately, it just happens."
Hansen's side pummelled a hapless Ireland side 46-14 in a match where the Irish self-imploded to gift the All Blacks countless opportunities from turnover ball along with a horror error rate. It would be a stark contrast to how clinical the English would be a week later.
"Then we played England who have been waiting for two and a half years to play this one game. Very, very desperate, right up at 100 percent, and if we are at 92 percent, that's a big shift. They came at us and played well and deserved to win.
In hindsight, Hansen believes the messages during the week may have been off, given the preceding win in the quarterfinal.
"I looked at myself, and the messages during the week and maybe they weren't on the money the way they could have been from a mental point of view, knowing that we have just come off a big win against Ireland."
Hansen also handed out some free advice for his imminent successor.
With just two candidates thought to be left in the running for New Zealand Rugby's top coaching job - Ian Foster and Scott Robertson - Hansen made it clear that whoever gets the role must be an incredible leader.
"Leadership is about influencing through relationship," Hansen told All Blacks TV.
"It's not about how much IQ you've got, it's about how much EQ [emotional quotient] you've got."
At one point Hansen illustrated that Foster - his assistant coach for the past eight years - may have an advantage over Robertson who has yet to play a part in the All Blacks coaching ranks.
"Understanding the environment you're in is going to be important, building relationships within that. Getting your team around you right [is] also really important, and what roles you want them to do."
Meanwhile, Robertson's strength of personality could help the current Crusaders coach make his mark in the role - as long as he doesn't change, Hansen said.
"By and large, the big thing is he's got to be himself. If he does that, then people will get in behind him."