Debutant winger Julian Savea scored a hat-trick in a 42-10 win for the All Blacks as Ireland had no answer for the pace and power of the world champions' backline.
O'Mahony, 22, making making his first international start at blindside flanker, acquitted himself well, winning two crucial turnovers as New Zealand swarmed forward, but admitted the tourists contributed to their own downfall.
"We're disappointed," O'Mahony said. "It was a different pace. The speed of the game was a lot quicker but we did ourselves no favours with the amount of turnovers we gave them.
"They are too good a team to be turning over ball to them that much.
"We don't have enough time to keep our heads down or beat ourselves up about everything. We have another Test Saturday and another opportunity. We go back to work.
"It was intense game and hugely physical throughout.
"We've got to cut down the amount of errors and look at our breakdown work. We'll have a look at it during the week and come up with a few things. They're a good side, but we'll be all right. We'll come back from it."
Jamie Heaslip also admitted costly turnovers and the All Blacks' impressive line speed were the two deciding factors in the match at Eden Park.
"The goal, the thing that everyone is chasing, is quick ball," said Heaslip.
"Their forwards provided a great launching platform with quick ball. With Dan (Carter) pulling the strings, they have really good guys that can hit it up in the middle as well as really good finishers with outstanding pace.
"If those guys can get consistent quick ball, it puts your defensive system under pressure. It was kind of hard, it was very quick at times out there and that's hard to defend against."
Ireland started off the first Test with some exciting, running rugby of their own, but they were often repelled backward and, in turn, spilled balls that the All Blacks pounced on.
"I think holding onto the ball rather than turning it over is the best way to play the game," Heaslip said.
"When we held on to it, I think, that we posed some questions and made some inroads in their defence, when we got reasonably quick ball. However, when it slowed right down, their line was set and it was hard to break it down."
New Zealand captain Richie McCaw spoke after the match about his side raising their level for next week's meeting in Christchurch and head coach Steve Hansen reflected on "a couple of tries we blew".
Heaslip added: "That is exactly why they are world champions, they set their standard like any other team.
"I'm sure Richie would be demanding more of their players like Brian (O'Driscoll), and the leaders of our team, would be demanding of our players in the coming week."
The number eight is aware of the significance of next Saturday's Test in Christchurch. It will be the first time the All Blacks have played in the city since it was struck by a series of devastating earthquakes in early 2011.
Heaslip said: "We had (former All Black) Brad Thorn over with us at Leinster for the last couple of months and, as much as what we heard through the news, it was great to hear from someone who had been there.
"(Ireland forwards' coach) Greg Feek, too, is somebody whose wife's family is from there as well. We had a one or two persons' removed experience of it all and we understand the emotion that will be going through there.
"It is a home of rugby. From my experience, as a guy outside of New Zealand, you always hear about games being played at Christchurch.
"It is going to be an epic occasion. You are going to have two teams going hammer and tongs at it and hopefully it will be a nice game to watch."
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