The 22-year-old playmaker was a last-minute inclusion in the starting side when playmaker Quade Cooper injured his calf during the warm-up at Perth Optus Stadium on Saturday night.
Lolesio says it may have worked in his favour, with little time to get nervous about the magnitude of his task as Australia strove to end an eight-game losing streak against the old foe.
After a shaky start with more injuries and a red card for lock Darcy Swain rocking the Wallabies, the five-eighth helped straighten up the attack to steer the side to a heroic 30-28 victory to open the three-Test series, heaping more pressure on England coach Eddie Jones.
His goal-kicking proved decisive, booting six from six for a personal haul of 15 points.
"I felt a lot more relaxed before I was told I was going to start which helped," Lolesio said on Sunday as the team prepared to fly to Brisbane for game two on Saturday.
"I was pretty shocked when Rens (Rennie) gave me the tap of the shoulder saying that I was starting.
"It's unfortunate for Quade, I know that would have been a tough call for him.
"I just grabbed it by the horns and tried to do my best for the team and it took me a while to find my groove in the game, but I'm just happy we got that win."
Lolesio was left shattered last month when a poorly-timed drop kick in the dying minutes was charged down, leaving the Brumbies just short in their Super Rugby Pacific semi-final against the Blues.
With nine Tests now under his belt, he was delighted to stand up in the big moments at Optus Stadium, rating it as a career highlight.
"I feel like I'm learning every game - I'm still so early in my career," he said.
"But I never want to be complacent and I always want to be willing to learn.
"Obviously that semi-final sucked and my professional rugby career has been a rollercoaster and it's pleasing...as a bright side."
Lolesio said it was also "pleasing" that Rennie backed him to step up in place of Cooper, ahead of veteran James O'Connor, who came onto the bench.
"I'm just very privileged that that he backs me but in saying that I've got to put the work in too.
"I can take confidence out of that but at the same time I won't be complacent because I know I've got to be a lot better, especially in that first half to put the team in a better position."
Cooper will undergo scans in Brisbane on Monday but was still limping on Sunday and looks unlikely to play in the Suncorp Test encounter.
The Wallabies allowed two late tries in the final three minutes which flattered the visitors and Lolesio said the end didn't sit well with his team.
"We were definitely disappointed with how we let those late two tries in because the scoreboard would have looked a lot a lot nicer so we will look at that defensively and we'll be better."
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