Australia were restricted to 243 in the first innings at St. George's Park and were bowled out for 239 in the second to give the Proteas an easy victory chase of 101 to level the series at 1-1.
While no Australian has managed a century, the home side has had two - rookie opener Aiden Markram scoring a gallant 143 in the loss in Durban and AB de Villiers setting the platform for victory at Port Elizabeth with an unbeaten 126.
"We haven't got a hundred so far in this series, so that's not ideal," Smith told Australian radio station SEN.
"Mitchell Marsh probably deserved a hundred in the first test to be fair, but if we're getting batters scoring big hundreds it certainly helps us out a hell of a lot. "Unfortunately, we haven't been able to do that so far in this series, but we've got a good opportunity to turn it around in the next."
After a rollicking home summer against England, the prolific Australia captain has also been down on his own lofty standards. His highest score was 56 at Durban and he was dismissed cheaply twice in Port Elizabeth.
Smith has scored only one ton against South Africa - an even 100 in his first match at Centurion in 2014 - and only three fifties in 14 innings against the same opponents since.
"I've played a lot more now since 2014 and the more you play, the more people have plans to you to try to keep you quiet and those kind of things," Smith said.
"It's just a part of batting, sometimes you have to work really hard for your runs and take a little bit longer, and some days you come out and things happen really quickly for you."
The four-test series resumes in Cape Town from March 22 and Australia will be glad for the extended break as all-rounder Marsh races to recover from a groin strain.
The Western Australian, who scored 96 in Durban, had a tough test at Port Elizabeth, battling a stomach complaint and dropping a catch in the slips.
He was also fined 20 percent of his match fee for swearing at South Africa fast bowler Kagiso Rabada, who was himself banned for the rest of the series for repeated code of conduct breaches.
"In regards to Mitch Marsh, it's a good break now between now and the next test match and he's telling me he'll be fine but we'll wait and see how things go," said Smith, who also gave a clean bill of health to Australia's pace trio of Mitchell Starc, Josh Hazlewood and Pat Cummins.
"I think all the quicks are going really well. I haven't heard today, but before today they were all feeling fine, so hopefully with a good 10-day break they can freshen up a little bit."
Australia battingDavid Warnerkagiso rabadaMitchell MarshPort Elizabethsouth africa vs australia 2018steve smith
First Published: March 13, 2018, 11:46 AM IST