The Autumn Nations Series came to an exhilarating conclusion as Smith landed a 79th-minute penalty to seize a 27-26 victory over the world champions at Twickenham on Saturday.
Apart from the thrill of toppling the Springboks against the odds, England produced their best performance since the 2019 World Cup, including a winning try count of 3-1.
And, although they were under siege for most of the second half, Smith was delighted with their willingness to continue attacking even as their 17-6 lead disintegrated before the boot of Handre Pollard.
“This game was massively special. We know how well South Africa have done this year and we got massively excited about it,” said the Harlequins fly-half.
“We built nicely through the week and to be able to perform for 80 minutes in front of all our loved ones and all the fans of England was amazing. We have to kick on now.
“We had to have the courage to keep playing because not many teams beat South Africa if you play them at their game.
“The coaches gave us the licence to be courageous and to have a go. It made my job easy and simple – just do your job and the rest will happen.
“We thought that we had to provide a different picture to South Africa and to do that we had to have courage. We really did have courage at times there.”
Smith calmly landed the decisive blow that completed a clean sweep of victories from the autumn campaign and maintained his own meteoric rise that is set to continue against Scotland in the Six Nations on February 5.
“It’s probably the highest pressure moment I’ve ever been been in, with the delay of it as well,” said Smith.
“The referee was checking things, so I had a lot of time think about it, but Courtney Lawes and Tom Curry and the leaders in the team put their arm around me and said, ‘We believe in you’.
“Maro (Itoje) said, ‘Take the whole minute’ and I didn’t do that. Sorry Maro! I was just collecting my thoughts. It was one of those kicks that…I used my breathing techniques which calmed me down and I focused on what I could control. I was very grateful that I sent that over.”