NEW ORLEANS — When the New York Knicks came to play the Hornets on Tuesday, J.R. Smith had the look of a man going back to his high school reunion, knowing he was going to meet the girl that got away.

Before the game, he looked remorseful, regretful — sad even. He admitted he sometimes thinks about what might have been in New Orleans, where he started his career in 2004 as the 18th overall pick, a 19-year-old just out of high school, a wondrous talent just needing to be molded.

“I do think about it,” said Smith, a 6-foot-6 guard. “The team we had could have been really a great team. We had a really great point guard (Chris Paul), a great shooting big man (David West), myself, a lot of good wins and a good coach.”

Smith constantly clashed with Byron Scott, then the Hornets’ coach. Scott does not have much time for rookies — certainly rookie mistakes and especially petulant, defiant rookies with no pedigree.

Smith, who passed on the University of North Carolina, one of college basketball’s most prestigious programs, rebuffed Scott’s insistence that he spend more time working on his game, that he earn the starting role and everything else he felt should have been handed to him. Worse, he made a mockery of it: His way of “working on his game” was taking half-court shots after practice.

In July 2006, the Hornets sent Smith to the Chicago Bulls in the trade that brought Tyson Chandler to New Orleans. Smith was traded to Denver less than a week later and continued the same act there: ridiculous shots, partying incessantly and making worse mistakes off the court than he did on it.

He was being a spoiled brat, acting out because he didn’t get what he wanted.

“I see things totally different now,” said Smith, adding that he wished he had listened to Scott. “Before, it was about me, me, me.”

Reality has a way of punching you in the face when you’re acting the fool. During the NBA lockout, Smith went overseas.

“Being in the NBA is a very spoiling experience,” he said. “Charter flights, per diems, nice hotels. Overseas, we often rode buses, stayed in hotels that were not what I was used to in the NBA, just the whole thing.”

Predictably, he had a falling out with his coach there, too. He came back to the NBA last season and finished out with the Knicks. When the year ended, he became a free agent.

He didn’t receive the offer he thought he’d get. That humbled him, especially coming on the heels of the overseas experience. It told him that he was the only one who thought he had game.

He had to work on that — and his attitude, too.

This season, back with the Knicks, Smith seems like a new person. He admitted that the New York nightlife got the best of him, and he knew it was time to stop playing the fool.

Eight years wasted was enough.

“As I get older, I start to care about things that are more important,” he said. “Winning, for one. Before, I was worried about money. Now, it’s more about team, winning and trying to get that (championship) ring.”

He is having his best season, and the Knicks are looking like contenders. All of his statistics — 15.5 points per game, 5.1 rebounds, 2.5 assists, 52.9 percent shooting on 3-point attempts, 43.8 percent on field goals — are up compared with his career averages. In the Knicks’ first six games, he averaged 18.0 points and shot a mind-boggling 73.7 percent on 3-point attempts, and early consideration for Sixth Man of the Year started coming his way.

Just as important, Knicks coach Mike Woodson said, Smith has used his freakish athletic ability to play excellent defense, an area he used to treat with disdain.

“He’s been able to play three positions (thanks to his defense),” Woodson said. “He can guard point guards; he can guard the two or the three. If there’s a mismatch, he’s feisty enough with big guys to try and hold them down until we can get back whole.”

That has earned Smith something precious in the NBA: minutes. He’s playing 33 per game compared to his career average of 24.3.

More importantly in his case, it’s an indication of something much better — trust, which comes from showing responsibility.

“I’m managing my time more wisely now,” he said. “Instead of being on the streets, I’m doing stuff that’s making me a better basketball player.

“Now, I want as many championships as I can get and just be the best person I can be.”