"There will be no excuses for us on Saturday night, we just have to make sure we pour everything into it. At the end of the 80th minute that's the end for us as far as our Lions rugby careers are concerned," said Mowen.
"You only get one crack at this. I can't even think about not having the cup with us - it would be crippling."
Mowen may have arrived on the international stage at the ripe old age of 28, but the man who couldn't make it at the Waratahs earlier in his career will return to Sydney as one of the stars of the series to date for the Wallabies.
Having kept Mike Phillips in check in the first Test in Brisbane, his line-out work was excellent in Melbourne and his high work rate in both games made him one of the stand-out players in gold.
"I knew that international rugby was going to be a step up and it hasn't surprised me how tough it has been. The Super Rugby tournament is extremely tough as it is and it gives you a good base," said Mowen.
"But Test rugby is the next level. The pressure you play under physically is massive, but emotionally as well. Knowing you are representing your country brings other pressures. That's the biggest difference to me - you wear that result for your country and that's the real big step up."
With the series perfectly poised at 1-1 the series decider at the weekend is going to be the biggest game in the careers of almost every player on either side. The atmosphere at the games in Brisbane and Melbourne was memorable, but Mowen is expecting every aspect of Saturday night's showdown to go up another notch
"It will be a huge step up in intensity. When you start the series there is still a chance that if you drop a game you can recover - there is no recovering from this one," he added.
"I know the Lions have spoken a lot about how it will be four years until they get to play again, and some of their guys won't play in another Lions series and want to play in a winning Lions series.
"But this is our only Lions series. We get to play them once every 12 years and some great Wallabies, like Nathan Sharpe, never got to play against them. We don't want our only memory of the Lions to be of losing the series to them.
"You've seen by the way the games have been decided by last minute penalty shots in both Tests that both sides are evenly matched. We have a good understanding of each others strengths and weaknesses.
"When you play each other three times on three consecutive weekends you get to know each other reasonably well. There will be one or two opportunities in the entire 80 minutes and it will be down to the side that takes them.
"We are in good shape, in really good shape actually. I feel fitter and fresher now than I did after the first Test and that says a lot about our medical staff and the way they have prepared the side."
The Wallabies have been working hard on the breakdown since their 16-15 win in Melbourne because, after an indifferent first Test, the Lions came roaring back in that phase last weekend with their now injured skipper Sam Warburton in supreme form.
"It's a question of refocusing for us at the breakdown. We probably got a bit lateral in our support lines in the second Test and we weren't giving them huge windows into the breakdown, but it was enough for them to make a huge difference and we certainly weren't happy with the number of times we turned the ball over," explained Mowen.
"That's something we've talked a lot about this week. They have lost Sam Warburton, who was huge for them last week, but they have two very good sevens to pick from, but it wasn't just the sevens were doing the damage. Out wide it was Murray on the ball or O'Driscoll - they obviously had a huge focus on it."