A late Anthony Laffor goal booked Sundowns a spot in the Cup quarterfinals with the Liberian forward slotting home a superb volley 10 minutes from time.
"I'll take this today [Friday]. It's a cup game," Mosimane said at Loftus Versfeld after the game.
"Even against Ajax Cape Town [Sundowns' first-round victory] we didn't play very well but we played the cup way.
"For the last two weeks we have been playing very well, the last two games we played well and we didn't win. Today, not too well but not bad but we won and I'll take the win.
"Winning is better than losing, the fans deserve it and that's football."
Sundowns found their rhythm last into the clash and applied plenty of pressure deep into the second period and were eventually rewarded in the 80th minute, when Laffor – a half-time replacement for Richard Henyekane – volleyed home from dead in front, having received an accurate delivery into the area which the Liberian controlled with his chest, before slotting past Gumede.
"It was an unbelievable goal," Mosimane said of Laffor's strike.
"You need to have guts and technique to score a goal like that. He even waited for the ball to come down inside the box with players around him.
"He showed he's an international player, maybe putting him on the bench helped him a bit and he came out smoking."
Having lost consecutive Premiership encounters, Mosimane added that Sundowns were fortunate at times after Arrows were denied by the woodwork on three occasions but believed his team deserved to advance into the last eight.
"The game was not short of opportunities, chances and excitement. They [Arrows] gave us a hard time, all the time.
"They were unfortunate. They hit the post three times. We didn't play as well as we played in our last two games, where we lost, but we won.
"It was difficult. They created a few opportunities but it's a cup game and we continue. I'm tired of playing well, counting the number of chances and losing. Today, we didn't create many chances and we won, it's part of football."
Turning his attention to the next round, Mosimane said he was relieved that the team bounced back from their run of poor league results and hoped the team could continue to work toward a cup triumph.
"The team needed a win. We needed to come back, nothing else, all we needed was to win and we got that.
"We deserve to win this cup and Sundowns deserve to get something and we will fight.
"Hopefully we reach the final, we think we can." – Sapa