The All Blacks squeaked home over the Springboks in a damp Wellington on Saturday night, winning 14-10, after being down 7-6 at the break.
The Springboks had their chances and in the last five minutes pressed the All Blacks hard but the men in black stood firm and held together.
Smith, who had a tough night at the office with a very physical contest going on in front of him, said the side never panicked when under the pump in the dying stages.
That calmness came from previous experiences which had seen the All Blacks get home in tight situations.
''I guess the biggest turning point for me was against Ireland last year. There was 30 minutes to go and Richie [captain Richie McCaw] was saying: 'We have got this boys, stay calm, trust our systems and it will work.' The belief from there has really gone up,'' Smith said.
''Now, you just go out there and do the plan as best as you can. Add a little bit of guts and do as best as you can. We have always said if a team is good enough to go through us or around us then so be it.
''But they won't beat us on spirit for the lack of trust. You won't get anyone going running out of the line to try and make a play. Everyone is trying to stay in the system, trust your insides and trust everyone to make a great decision.''
He said the All Blacks had calming voices, experienced captains from Super rugby teams, who steadied the side when it was under pressure.
''To be honest, it is really simple. Just the way they communicate. Just keep it really simple. It calms me. Keeps me really calm and backing our systems in the end.
''We do not like losing. This is our last game of the year on our own soil and we had talked about that all week. That little silver fern on your chest gives you strength and makes you work a bit harder.''
The All Blacks went ahead early in the second half when McCaw went over in the corner, after Kieran Read had expertly caught an Aaron Cruden cross kick.
The home side held out in the dying stages as the Springboks' route one tactics came up short.
The match was physically torrid, with plenty of handling errors due to the pressure of the defence and the slippery ball.
The All Blacks lost Ma'a Nonu at halftime with a broken arm and he has been ruled out of all rugby for the rest of the year.
All Black coach Steve Hansen said fellow midfielder Ryan Crotty should be right to come back next match, having recovered from a facial fracture.
Hansen ruled out starting Ben Smith at second five-eighth in a test. He had replaced Nonu at second five-eighth in a test last year, so it was not a totally new experience for the Otago man.
Hansen was happy overall with the performance, saying the character of the side came through, although he felt the kicking of his team could have been a lot better.
''We kicked at the wrong time and in the wrong areas at times. It was just one of those nights when we could have kept the ball a bit more, or put it more into the corner than into the middle of the park,'' Hansen said.
''The character of the side has been tested a few times over the last couple of years and they keep coming with an A-plus pass mark.
''Once again we did that again. We put ourselves under pressure at times with out kicking which allowed the Boks to attack us ... but we showed a lot of courage to keep them out.''
The All Blacks disbanded yesterday and will come together next weekend to begin the long haul to Argentina.
They play the Pumas in La Plata on September 28, before taking on the Springboks the following week.
All Blacks v Springboks
The scores
All Blacks 14
Richie McCaw try; Aaron Cruden 2 pen, Beauden Barrett pen
Springboks 10
Cornal Hendricks try; Handre Pollard con, drop goal
Halftime: Springboks 7-6.
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