The teams are locked at 1-1 after the Springboks kept themselves in the hunt last weekend.
Lawes and Saints team-mate Dan Biggar have started both Test matches so far - and they will both be in the first 15 again in Cape Town this weekend.
And Lawes said: “It’s going to be tough and there needs to be a conscious effort to stay out of that dog fight and niggle because I imagine that’s what they’re going to want to bring again.
“We need to make a conscious effort to leave it alone and get back to what we want to do, which is trying to bring tempo to the game.
“They can throw the handbags around as much as they like as long as we can get that ball out and play some rugby.
“We can’t get too caught up in the niggle and scrapping because it just slows down the game and it doesn’t really help us.
“We like a high-tempo game – we are a fit team, we want to run around, we want the ball in hand so we need to to try and speed the game up as much as we can.
“If we can do that they are going to struggle to keep up with us and it affects their scrum and maul as well.
“They came with a clear game plan last weekend and that was to slow the game down. Their strategy paid off – they slowed it down.
“When they are not tired they are going to scrum well and because they are big, strong men they are going to maul well.”
Lawes knows how much it would mean to finish the series in style on Saturday.
“We have given an awful lot to this tour, and for each other and it means a great deal to us. We have to go out there and express ourselves and show that.
“Tours are always the same. They feel like you’ve been there forever but they fly by at the same time.
"It’s very strange but one last big hit and then it’s all done. That makes it easier to put it all out there and give everything you’ve got.”