The 34-year-old Doolan, who waited tables and fixed poker machines in her native Australia while working her way into professional golf, proved it on Sunday.
Doolan shot a 5-under-par 65 in soggy conditions to win the LPGA Tour's season opener by three strokes.
''I hadn't felt it until the last six months, but I've tried to believe in that for quite a while,'' she said after capturing her second title, the Welch's-Fry's Championship.
Doolan won $120,000 -- nearly half of her 2002 earnings -- with her score of 21-under 259.
''I've seen the girls shoot 20-plus under par,'' she said. ''I never knew I was going to do it, but I did it today, and that's something that I feel really good about.''
Doolan held up under pressure. She ignored the leaderboard and responded to a discouraging bogey with a birdie on the next hole to blunt charges by Grace Park and Betsy King down the stretch.
On the 18th green, she asked her caddie if she needed a birdie to win. He shook his head, and she made a routine par.
King carded a 65 to tie third-round leader Lorie Kane (70) at 262.
''On 17, I had a 12- or 15-footer that I wimped on,'' King said. ''I haven't been up there for a little while, so my putting stroke today was not as fluid.''
Park, derailed by a double bogey on the 17th hole, settled for a 67 and a tie with Christina Kim (70) at 263.
Kim, trying to become the first rookie to win her LPGA debut since Beverly Hanson in 1951, also had late bogey problems.
Meg Mallon fired a 70 for sole possession of sixth, five shots off the lead.
Mallon had a 60 on Friday, the second-lowest round in LPGA play, to lead at the midpoint. But she was only 6-under in the other 54 holes of the tournament.
Doolan had a career-low 62 on Friday. And what has commonly happened during her career, another player grabbed the spotlight.
But Doolan, whose breakthrough victory came two years ago in Dayton, Ohio, in a five-hole playoff with Wendy Ward, was not to be denied this time.
She overcame two bogeys with a seven-birdie effort, starting on the first hole.
Doolan dipped to 20-under on No. 14, where her approach shot came up short of the green after a brief pause to put on a sweater during a rain squall. She chipped five feet past the flag and missed the comebacker.
Then she responded with a 12-foot, downhill birdie putt on the next hole and parred out while the competition faltered.
Kane seemed poised to make a run when she birdied the 16th hole. Instead, she gave Doolan the last bit of breathing room with a bogey on No. 17, falling three shots back.
Kane said it was never that close.
''My game plan was to birdie the last five holes,'' Kane said. ''I knew I had to make at least three or four to have a chance. And so, standing on 17, I was thinking I needed to make a 1.''
Park, who got within one stroke at 19-under on No. 15, took a disastrous double bogey-5 on the 137-yard 17th when her tee shot landed in a bunker and she three-putted from 12 feet after blasting out of the sand.
The race was tight at the start, as Kim made up her one-shot deficit on Kane with a birdie on the first hole.
By the fourth, though, Doolan got her third straight birdie and took the lead. She also birdied No. 6 to go 20-under and went up by two shots.
That lasted long enough for Kim to reach the sixth green, where she rolled in a birdie putt to reach 19-under.
Doolan gave back a shot with a bogey on No. 7, but Kim followed suit when her putt from the fringe to save par rolled three feet past the cup, and Doolan went two strokes ahead again with a seven-foot birdie putt on the eighth hole.
On the pivotal 12th hole, Doolan got her sixth birdie of the round and went up by three shots when Kim two-putted from 4 1/2 feet and bogeyed.