Joe Schmidt's men will feel the repercussions of Sunday's New Zealand heartbreak for some time, after letting a 22-7 lead slip away.
The All Blacks tiptoed to a converted try in overtime to ghost home 24-22 and secure the much-vaunted perfect season that eluded them in 2012.
The crushing capitulation has sparked debates on whether failure is hard-wired into Ireland's sporting DNA.
But Leinster openside O'Brien said it is time Ireland shrugged off that nearly-men status, and the inconsistency that has dogged their last two years.
Ireland still wait for that first victory over New Zealand, Sunday's misery adding to their slender 22-19 defeat in Christchurch in June.
One week after pushing the All Blacks all the way in the summer, the Kiwis swatted Ireland aside in a 60-0 record victory.
It is precisely such fluctuating form that has O'Brien challenging Ireland to mature, and fast.
"Lads will have to have a good look at their game; what we did well and didn't do so well," he said.
"I think we can improve on that performance.
"We were obviously annoyed after Australia (losing 32-15 10 days ago), and that fuelled the fire, along with the day that was in it - history and whatnot - but I think it's time the lads grew up and know what's expected when they put on an Irish jersey.
"If we bring that intensity and work-rate that we had at the start of the game into the Six Nations, then we'll be in a good place.
"We've set standards in the past and this is one of those, but we've to make sure we kick on from there and make sure that's there every day in the Six Nations."