India chased the 287-run target with two balls to spare at the R Premadasa Stadium.
"I learnt over the years, how to bat when you need eight an over, Gautam played very well early on, set the platform. I looked to play straight, not to play cross, I knew I could hit over cover, over mid-wicket, I also wanted to run hard. Credit goes to Gautam, he batted very well," Raina said.
Raina was named the Man of the Match for his 65 off 45 balls, innings that included six boundaries and a six.
India skipper Mahendra Singh Dhoni was fulsome in his praise for Raina and Gambhir, and said he always believed that the team could win.
"We had a chance, because Gautam was still batting, and we all had belief in Raina, we also had Irfan and Ashwin.
"I think those two wickets changed the game, Gautam did really well, we needed one of the top three to put in a performance like this," Dhoni said at the post-match presentation ceremony.
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He was, however, a bit worried over his side's bowling at the death overs.
"We need to improve our death bowling, and our fielding, but overall I was happy with our performance."
Rival captain Mahela Jayawardene felt his bowlers could not put enough pressure on the Indians.
"It was one of those days. They are a quality team, I thought we played a good game, just a few mistakes. Up front, we were not putting enough pressure in the chase.
"We bowled poorly (towards the end) and dropped Suresh as well. It's tough when you lose, but you try and re-focus for the next game. Sanga will get a good deserved break (the batsman has been ruled out owing to a finger injury)."