Villa's 100 per cent start to the campaign was ended at Villa Park by Leeds United, with Patrick Bamford firing home a hat trick to ensure Dean Smith's side didn't go top of the table.
But Cash is keen to right the wrongs from that performance, and believes Villa are ready to respond on the pitch.
"It was a tough game, Leeds are a really good side, they move the ball really quickly and they like to take players out of spaces, which they do really well." Cash said.
"I played against them in the Championship and the way they did it the other day it was really tough for us.
"In football, you win, lose and draw games - so you can't look at it as a negative. When you win games you can't get too high and when you lose them you can't get too low. Luckily we've got a game this weekend to bounce back and show some real character.
"The reaction from the group in training has been really good and that's all you can do after a defeat, try and reflect and then bounce back on the training field and get in good spirits again."
Villa had won their four previous league games in the 23-year-old's first season in the top flight - and he says that the players cannot feel sorry for themselves after a single defeat.
"We've won four out of five games, which is brilliant in this league, so we can't feel too sorry for ourselves, we've got to move on and we've got a massive game on the weekend.
"They're a good side [Southampton], obviously every team in this league is a good team so we've done some analysis on them on the training pitch and how they play - I've no doubt we'll be ready for it."
The defender has quickly settled in at Villa Park, quickly cementing a starting spot under Smith, having made the move from Nottingham Forest over the summer.
He says that the atmosphere around the club has helped him gel quickly at B6 and that it's a team he's enjoying playing within.
"It's been a really good couple of months. We're five games in now and won four - and obviously lost at the weekend, but it's been a fantastic start from the lads and I've settled in really well." he said.
"We've got a great group of lads, great staff and every day on the training ground we're working really hard and the banter around the group is really good so they've made it nice and easy for me to settle in.
"It's been good. We're taking every game as it comes, obviously it's my first season in the Premier League and I feel like I've adapted well.
"I've just got to keep going, we're only five games in so hopefully in 30 games I can be sitting here saying the exact same thing.
"But I've enjoyed every minute of it so far and long may it continue."
Having converted from a winger to the right back position, Cash says that it's a challenge he'd embraced even more since joining Villa - as he relishes coming up against some of the best wingers in the game.
"No disrespect to the quality in the Championship, but the wingers you're coming up against in the Premier League are the next level. The pace, sometimes is really hard to deal with but I back myself in one v one situations and that's what you've got to do." he said.
"You've got to train hard in the week and then when it comes to the weekend you've got to know that you're ready and I feel like I'm doing that. I like a challenge and it's going good so far.
"My game now obviously as a full back is to get as many tackles and interceptions as I can as well as the stuff going forward, but first things first for me is my defensive side.
"I've got to clean sheets, and we've done that this season.
"As a defender there's nothing better than winning a game and having a clean sheet. It's almost our job done and the forwards' job done scoring the goal.
"In training every day with JT we're working really hard defensively as a unit. Obviously the four of us and Emi, as well as the other players that haven't been playing, the way we've defended as unit this season has been brilliant.
"We're really hard to beat and we've got to keep taking positives."