The 45-year-old Englishman beat JJ Spaun in a play-off to take his first PGA Tour title in more than two years and he admitted the tournament's final hours, which saw the pair take part in three sudden death holes, was "amazing".
He said afterwards: "That was an amazing last 90 minutes.
"I never stopped believing. I played unbelievable golf coming down the stretch. I had so much fun with it.
"When I bring my best I know I'm good enough to play, to compete, and now to win against the best players in the world.
"It's a very gratifying day for me and a lot of hard work coming to fruition.
"I feel like there could be a good run of golf [for me] still. I can't let my age become too much of a story but today is huge for me."
Fellow Brit Tommy Fleetwood had gone into the final round with a one-stroke lead but ultimately tied for third with Scottie Scheffler, and despite his disappointment, the 34-year-old golfer found some positives in the tournament.
He said: "I'm getting close, that's the good side of it. On the back nine, I managed to get myself ahead, played some really good golf, putted really well.
"Justin and JJ have done great there and I just didn't do enough.
"I'm obviously disappointed. I was right in there with a chance, and it's hard."