HUMBLE, Texas (AP) -- Hunter Mahan doesn't dwell on bad shots anymore, and he says that's leading to more good ones.
Mahan shot a 1-under 71 on Sunday to win the Houston Open, edging out Carl Pettersson by one stroke and becoming the first two-time champion on the tour in 2012.
The 29-year-old Mahan finished 16 under for the tournament and moved to No. 4 in the world ranking, the first time he's ever been the highest-ranked American.
"That's a pretty surreal thing to think about," Mahan said. "It shows me what I can do, shows me what I'm capable of."
The 29-year-old Mahan feels as if he finally has the mental approach to match his physical skills. He credits Canadian sports psychologist Jim Murphy with teaching him to enjoy the game more, and that's led to better results.
"It's easy to let your mind run wild and get down on yourself," Mahan said. "That's what I used to do. I'm trying to pump myself up more and just believe in myself."
Mahan earned his fifth career victory. He has six top-25 finishes in seven starts this year, including a victory over Rory McIlroy in the final of the Match Play Championships in February.
"You've got to enjoy this stuff," Mahan said. "It's kind of an honor and a pleasure to be in these tough situations. This is what you work for, to be in these fun, tough, tight situations."
The new attitude got another pressurized test on Sunday.
Standing on the 18th tee with a one-stroke lead, Mahan confidently hit his tee shot down the middle of the fairway, then knocked his 203-yard approach to 21 feet. He gave caddie John Wood a high-five when the ball landed safely on the green.
"Absolutely awesome," Wood said.
The tournament became the run-up event to the Masters in 2007, and Mahan has never felt better about his game heading to Augusta.
"I feel very capable of playing great golf, and I feel like I showed myself I don't have to be perfect to win," he said. "That's a great thing to feel, for sure."
Pettersson (71) finished with eight pars for his second runner-up finish this year. Third-round leader Louis Oosthuizen (75) was another shot back at 14 under.
Mahan began the day two shots behind Oosthuizen, who lost the lead with two double bogeys on his front nine.
Defending champion Phil Mickelson (71), Keegan Bradley (71), Brian Davis (74) and Jeff Overton (68) all finished 12 under.
Three-time major champion Ernie Els finished 10 under and fell short in his bid to earn an automatic invitation to this week's Masters. Els needed a victory to avoid missing Augusta for the first time since 1993.
"It's not going to change my life, either way," Els said. "I've played many out there. It's one of those things."
The Masters could offer a special invitation to Els, like tournament officials did for Greg Norman in 2002.
Els has played well this year, earning top-five finishes at the Transitions and Bay Hill. But he said Sunday he would decline an invitation if he received one at the last minute.
"To go through all of this, and then get an invite, I wouldn't take it," he said. "They can keep it."
The problems for Oosthuizen began with a three-putt on No. 2. He holed a downhill 45-footer for a birdie on No. 3, but hit his tee shot on No. 5 into a divot and missed the green with his approach. He botched a chip and two-putted from 20 feet.
Oosthuizen pulled his approach to the par-5 8th into the native area, leading to his second double bogey.
"I'm not going to be bothered about the way I played the front nine," Oosthuizen said. "I had a few horrific lies and bounces. It happens."
Mahan parred the first eight holes, then finally took advantage of Oosthuizen's collapse with a 5-foot birdie putt on No. 9. Pettersson missed a 19-foot par putt on No. 10, leaving Mahan in the lead by himself at 16 under.
Mahan found a greenside bunker on No. 14 and bogeyed, then hooked his tee shot to the 204-yard, par-3 16th. He pitched onto the green, and the ball rolled down a slope to within 16 inches for an easy par.
"I thought it was going to be good," Mahan said, "but a tap-in there was huge."
Pettersson left an 18-foot birdie putt short on the 488-yard 18th, the hardest hole on the course, with a pond running down the length of the fairway on the left. Like Els, Pettersson needed a win to earn a trip to Augusta.