Pakistan were 242 for five at the close, with captain Inzamam-ul-Haq unbeaten on 35.
Younis, the first of three men in quick succession to get out hooking, said his 133-run third wicket partnership with Yasir Hameed had put Pakistan in a reasonable position.
"It happens in Test cricket. You lose one wicket and then you lose two or three," said Younis.
"The main thing was that after we lost two wickets early on, me and Yasir played a little bit of aggressive cricket, not on the back foot. On these type of pitches you must be the aggressor, especially against a side like South Africa who are always coming at you in your face."
He said it was a good batting pitch, a good toss to win and added that Pakistan would be aiming for a total in excess of 350.
Khan said the first hour on the second day would be crucial, with Inzamam and Kamran Akmal resuming against the second new ball, which is just three overs old.
"If they can get through the first hour we can make 350 plus," he said.
South African wicketkeeper Mark Boucher, who set a new record of 367 Test catches, agreed that 350 was a benchmark total on a pitch which he felt was "a bit two-paced".
Boucher said he expected the pitch to get better for batting.
"Picking up three wickets in the last session was a big bonus for us. The game's probably on an even keel."