Serena Williams needed just 61 minutes to capture her eighth title of 2013 and the 54th of her career, which moved her past Monica Seles into sole possession of ninth on the WTA career list in the Open Era.
But she said the lopsided win belied the difficulty of winning any title.
"No tournament is ever easy, especially being in the position I am in," Williams said.
"The tournament starts and they expect you to win. The tournament is like, 'Well, you're going to be in the final. After your semi-final I want you to do this, and you have to do this and this....
"Who knows if I'll even make it to the semi-finals? It's a lot of pressure and it's not easy."
The 31-year-old American, stung by a fourth-round Wimbledon exit after grabbing her 16th Grand Slam crown at Roland Garros, claimed a third Canadian title to go with those she won in 2001 and 2011.
It was a perfect prep for her defence of the US Open title, with Williams hoping she can put her Australian Open and Wimbledon disappointments behind her when the last Grand Slam of the year begins on August 26.
"I'm disappointed I didn't win Wimbledon or Australia," said Williams, who is slated for one more hardcourt tuneup at Cincinnati next week. "I'm always insatiable."
Her formula for attacking Flushing Meadows, the venue of the US Open, is simple: "Stay positive ... stay hungry and just stay aggressive".
Cirstea, who had beaten three top-10 players en route to the final in Caroline Wozniacki, Petra Kvitova and Li Na as well as former world number one Jelena Jankovic, couldn't pull off another upset, although Williams acknowledged the 23-year-old Romanian's run had caught her attention.
"I know she's so capable of winning big matches," Williams said. "And she's had so many big upsets this week. I didn't want to be another casualty."
In the end, however, it was never close as Williams handed Cirstea a third straight-sets defeat in as many meetings. Cirstea has never managed to take more than two games off Williams in a set.
Despite her growing confidence, Cirstea's nerves betrayed her as she opened the match with a double fault, and delivered another double to surrender her serve in the first game.
On the verge of another break in the third game, she produced her best rally of the match to keep Williams at bay briefly, but the American gained the break on her third opportunity for a 3-0 lead.
"I actually think the start was not as bad as the score showed," Cirstea said. "First three games I actually had really good chances in all of them, so I could have been up 3-0."
An on-court discussion with coach Darren Cahill at the changeover energized Cirstea. She broke Williams at love and held to narrow the gap to 3-2, but the magic didn't last.
Williams won the last three games to pocket the set in 37 minutes.
Another pep-talk from Cahill at 3-0 in the second set couldn't help Cirstea, her only flash of resistance coming when she saved a first match point, only to smack a forehand wide on the second.
"She got better as the match went along," Cirstea said. "I was not able to pick up my game as I was in the past few matches.
"I actually played probably the best game of the match at a set and 5-0 down, but all credit to her. There is a reason why we have a ranking and why she is on top of that ranking.
"She's the number one player and she's proving that every single time she steps on the court."