Springbok wing Kurt-Lee Arendse upended Barrett in an illegal charge that resulted in a four-week ban in the 10-26 loss for the All Blacks.
Barrett told All Blacks TV he immediately feared the worst in the collision.
After landing on the ground, All Blacks support staff were quick to his side.
"I can't remember who told me to stay still.
"It wasn't until Doc came on and asked me, 'could I move my fingers and toes?'
"I was relieved I passed all those tests and eventually sat up and was able to walk off.
"There was a fearful period there for a minute or so when you think of the worst.
"It's quite scary when you go over backwards and find yourself come down on your head and shoulders.
"It's part of the game and, every time we go up for the high ball we've got to be courageous," he said.
Chasers of the ball sometimes made errors in judgments.
"They have intentions to get up but find themselves running into the person, which happened at the weekend.
"As escorters, the players in front of me are doing their best to protect me, but it's not always the case."
Barrett said the high-ball collisions and contests were not unexpected when playing South Africa. In those 50-50 situations, South African players would look to make a contest, and it was up to the All Blacks to continue to compete.
"Our escorters have to do a job to legally stop that chaser from running a good line and allowing that mid-air collision."
Barrett had suffered previously in such a collision against France in 2018 at Wellington. On that occasion, he landed on his shoulder and escaped serious injury.
"It's high-speed, split-second stuff which can be quite dangerous.
"I was lucky on that occasion and was lucky at the weekend."
He hoped his luck could hold in the future because it was a tactic South Africa would continue to employ.
"It's a strength of South Africa's because they cause carnage up in the air and they like to play off the spills," he said.
The 105-Test veteran has been able to train with the side and is expected to be available for the second Test at Johannesburg on Saturday.
Barrett said there was no lack of motivation among the All Blacks.
"We believe in what we're doing and where we're heading. Winning is a habit, but losing can be too.
"We've just got to remember how well we can do the simple things, why we play the game, and what got us here in the first place," he said.
It was about not over-complicating things, shutting out external noise and playing rugby.