Matias Grez

(CNN) -- Few 21-year-olds will have had a better weekend than Aaron Wise.

The American scooped a bumper $1,386,000 after winning his first ever PGA Tour title at the AT&T Byron Nelson tournament in Dallas.

Wise, who was tied second behind Jason Day at Quail Hollow earlier this month, shot a closing 65 to reach 23 under and beat experienced Australian Marc Leishman by three shots.

The South African-born Wise tied for the lead after three rounds, and suffered a fitful night's sleep as his mind wandered to "what ifs?"

His focus wasn't helped when he received a text in the gym Sunday morning to say there would be a four-hour rain delay at Trinity Forest. As he tried to fill the time, his mother Karla further cluttered his thoughts with the benefits of a first PGA Tour win. Wise had to take action.

"I kind of made her leave the room," Wise told reporters.

"She went and did her own thing for a little bit. I was able to kind of stop thinking about it, get back into the zone ... it was kind of business for me after that."

'Huge'

As he sunk his final putt for par in near-darkness, Wise became the second-youngest player to win the prestigious Byron Nelson -- behind only Tiger Woods.

"I don't think I'm anywhere near my prime, I hope, and for me to be able to get all this experience so early -- it's only going to help me down the road when I'm contending in a lot of golf tournaments," he told PGATour.com.

As well as a sizeable cheque, the victory gave Wise a two-year exemption on the PGA Tour, meaning he doesn't have to earn a certain amount to retain his playing privileges for next season.

"It's huge at a young age to be able to plan your schedule, to be able to get into all the big events, to get that experience," said Wise.

"You look at guys like Jordan (Spieth), Rory (McIlroy), JT (Justin Thomas), how it's just paid off for them when they're 24, 25, kind of hitting their prime a little bit and get all that experience already.

"They're able to win so many golf tournaments and I look at this as kind of helping me do that as well."

World No.3 Jordan Spieth, playing in his home tournament, finished at 11 under in a tie for 21st alongside defending champion Billy Horschel.

Spieth became the youngest PGA Tour winner in 82 years when he clinched the John Deere Classic as a 19-year-old in 2013.