The Reds started at an incredible pace at the Suncorp Stadium and looked set to finish on a real high when Nick Frisby scored their second try with 15 minutes left, but The Lions dug deep to ensure they remain unbeaten in 2013.
"If you're tired then you shouldn't be wearing the jersey, it's as simple as that," said North.
"When it comes to fitness, it's a case of putting one foot in front of the other and keeping moving forwards. You have to keep going.
"Sure, there's been a lot of travelling but that's what a Lions tour is all about - it's a lot of travelling and a lot of rugby."
North was in brilliant form in Brisbane as he regularly broke the Reds' defensive line in a free-flowing affair.
The 21-year-old Scarlets star produced a sensational solo run that almost resulted in a try for skipper Sam Warburton and was constantly a threat in his second start and third appearance of the tour.
Plenty of praise has since come the youngster's way but, while he admits he was pleased with the impact he made after coming on as an early replacement for Manu Tuilagi, he insists improvements have to be made all round as far as The Lions are concerned.
"I was happy on a personal level but, as a squad, we have to look at the game and come back that bit stronger," added North, who hopes The Lions will continue to play with the ambition they showed at the weekend.
"Initially when you come on you try and make a difference, that's just the way of it. You try and up the tempo and take the game to them a little bit. I came on and did my job really.
"We knew it was going to be a tough match and so it proved. They came at us with some pace right from the off but, to be fair to the boys who were in there, they dug in. We got our noses in front but we were worked hard for sure.
"The momentum is good and, after Saturday, it's a case of we know what's coming.
"We'll be far stronger for the experience and we'll make sure we're not on the back foot for the first 10 minutes again. The pace has picked up and we just need to start stronger.
"Australia will play a fast game and we need to make sure we run hard back at them. We don't want to be known as just physical guys. We want so show some finesse and mix it up a bit. We need to play as hard as we can but we also want to play with a bit of style."