The Saints had looked well on their way to European glory when they secured a 22-6 interval lead. The Premiership side ran in three tries, on the back of a magnificent scrum platform, through Phil Dowson, Ben Foden and Dylan Hartley.
But Leinster produced an almost flawless second-half performance as the superb Sexton ran in two tries and kicked 12 points, with Nathan Hines grabbing a third score, to clinch a remarkable win in what must rank as the best Heineken final to date.
O'Driscoll told Sky Sports 1: "We had some choice words at half-time. We knew if we could hold on to the ball we had them in trouble.
"There were some inspirational words from Jonathan at half-time which picked us up, he was a man possessed. He said this game would be remembered if we came back and we will remember this for a long time.
"We knew we had that (second-half display) in us. We played against a tough opposition but we knew if we held on to the ball we knew we could create chances."
But the Ireland legend was at a loss to explain how his men had been so poor during the first stanza.
"We coughed up so much ball, but that was the difference. In the second half we held on to it and the passes stuck as well," he said.
Matchwinner Sexton, whose personal haul of 28 points was just two short of Diego Dominguez's record for a Heineken final, refused to take too much credit for his half-time team talk, but said: "We were shellshocked and we needed half-time. We regrouped.
"I'm a bit of a nerd when it comes to sport and I said that we see in sport that teams can come back like Liverpool [in the 2005 Champions League final] a few years ago. Stuff like this happens. We had to believe and we took our chances."
Northampton director of rugby Jim Mallinder felt his side's fatigue after their bruising Premiership semi-final loss at Leicester had been a factor in their defeat, especially as Leinster had been able to withdraw some key players during their more comfortable Magners League semi win over Ulster.
"We were tired, you could tell at half-time," he said.
"It was just a case of telling the lads to dig in for just 40 more minutes but the long season took its toll in the end.
"It was a full on game, it was very fast and credit to all the players involved."
Mallinder withdrew the likes of Soane Tonga'uhia and captain Dylan Hartley as his side trailed in the final quarter, and he said: "It was because they were exhausted.
"They were shot. It would have been nice not to have had a full-on game last week, and Leinster managed to take their five best players off in their game. We could not do that against Leicester.
"But we will come back stronger. We have always improved and we have said, in the huddle at the end, let's see if we can win it next time."
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