The Proteas fell to a damaging 214-run loss in the series opener in Durban, but then outplayed the tourists for an innings and 31-run victory in Gqeberha.
Harmer played a crucial role in the win at St George's Park, scoring a career-best 82 batting at number 9 before taking two wickets in the second innings as the Proteas levelled the series at 1-1 in the three-match series.
He said after the victory: "To be 1-0 down and to be able to turn it around and then to be 40-4 and be able to turn that pressure and put it on them and then to realise that actually they are human and if we bowl well and put them under pressure, there is the possibility that we can get on top of them, was really nice to see.
"Durban was a tough few days for us with our backs against the wall and there was nowhere to go. It was nice for us to turn it around and to be able to put them under pressure.
"There was a lot of motivation and fire burning in the belly of a lot of the boys that we didn't put our best foot forward and that we didn't lose on our terms in Durban.
"As a spinner, I love scoring runs. I feel like taking wickets is my job, but I get a lot more gratification from scoring runs."
The 37-year-old insists though that the Proteas must remain grounded as they look to seal series in Cape Town, with the deciding Test starting at Newlands on Tuesday.
Harmer praised the close-knit environment that has been established in the South African squad.
"Without a doubt, it's one of the best dressing rooms I've been a part of," Harmer said. "Everyone's invested, everyone's pulling in the same direction, and it's a really fun group to be around.
"There's still a lot of cricket to be played in Cape Town, so we take the positives from this, make sure we learn from our mistakes, and put our best foot forward."
South Africa produced a dominant performance to beat Australia by an innings and 31 runs in the second Test at St George's Park in Gqeberha on Thursday, levelling the series at 1-1.
South Africa produced a commanding performance to defeat Australia by an innings and 31 runs in the second Test at St George's Park in Gqeberha, with captain Temba Bavuma leading the way with a magnificent 179.
Marco Jansen took a five-wicket haul as the Proteas skittled Australia out for just 99, before the tourists found themselves in trouble following-on at 156-4, still trailing by 170 runs.
Proteas captain Temba Bavuma struck his fifth Test century, and the best of his career, as the hosts dominated Australia on the third day of the second Test at St George's Park in Gqeberha.
