That is what made Sunday’s defeat at the hands of the underdog New York Jets so painful. A city where a baseball team’s 86-year World Series drought largely defined the sports psyche for generations is now so awash in sports success that the biggest shock comes when our professional athletes fall short. In fact, that awareness of being the favorites made many fans anxious during all the trash-talking that led up to the game.

“I don’t know if you call it fatalism or Irish Puritanism,’’ said Boston College historian Thomas O’Connor, who had a gut feeling the Patriots would lose despite being favored by 9 points. “There was always the idea ingrained in you by the Sisters of St. Joseph, by the parochial schools, that you mustn’t get too big for your britches . . . Losing a sense of humility will get you in the end.’’

Coach Bill Belichick and company can hardly be accused of losing their humility, largely refusing to respond to the Jets’ taunts before the game or blame anyone but themselves afterward. Belichick congratulated the Jets’ trash-talker in chief, coach Rex Ryan, immediately after what had to be one of the most painful defeats of his storied career.

But after a decade of unprecedented success, Boston sports fans may have grown too accustomed to the view from the top. Since the 2000 season, no team has won more Super Bowls than the Patriots, who won it three times, and 25 NFL teams didn’t lift the Lombardi Trophy once. But, yesterday, gloomy Patriots fans seemed more concerned that the last Patriots championship came in 2005 and the team hasn’t won a playoff game since Eli Manning’s last-minute pass led the New York Giants past the previously undefeated Patriots in Super Bowl XLII in 2008.

“I feel like a lot of people around here are really getting spoiled,’’ said Dan Topliffe, an 18-year-old student at Framingham State University as he visited Faneuil Hall yesterday. He said the Patriots’ performance on Sunday will reinforce the belief that they are a “playoff choke team.’’

Patrick Ingram, shopping at Patriot Place in Foxborough next to Gillette Stadium, agreed that Boston sports fans are spoiled. He noted that most of his friends left a game-watching party on Sunday before the two-minute warning, seconds before the Patriots pulled within a touchdown of tying the game.

“When you have the successes like we’ve had recently, you don’t accept losing easily,’’ said Ingram, 28. “We all went on the same ride this season and all of a sudden, it’s like, ‘Stop and get off. Ride over.’ ’’

It’s hard to imagine Boston fans of the past feeling a sense of championship entitlement unless they cared only about the Celtics, which won an astonishing nine of 10 NBA championships in the 1960s. From 1960 to 2000, the other three major sports teams won a total of two championships, both by the Bobby Orr-led Bruins in the early 1970s. The Red Sox, who hadn’t won it all since they sold Ruth to the New York Yankees in 1919, often were so frustrating that they inspired dark humor passed down among generations of fans: “The Red Sox killed my father, and now they’re coming for me.’’

But the Patriots’ hiring of Belichick on Jan. 27, 2000, marked the beginning of a better era for the Patriots and the other Boston teams. On Feb. 3, 2002, Adam Vinatieri kicked a dramatic field goal as time expired to give the underdog Patriots their first NFL championship. More than a million people came to the rally to celebrate Boston’s first major sports championship since 1986.

Since then, the Patriots have won two more Super Bowls, and the Red Sox broke the 86-year “curse of the Bambino,’’ taking the World Series in 2004 and again in 2007. The rejuvenated Celtics brought the NBA championship back to Boston in 2008 and came within 4 points of winning it again last season. The Celtics and Bruins are having successful seasons, and the Patriots had the best regular-season record in the NFL.

Far from satisfying Boston fans, success makes many of them anxious. Jason Baker, a New Hampshire guidance counselor and diehard Patriots fan, worried for weeks that the team was not nearly as good as its 14-2 record suggested. He felt they were living on the strength of Tom Brady’s arm and scoring enough points to offset an untested defense. Never mind that they had pummeled the Jets, 45-3, just six weeks ago, Baker had a bad feeling heading into the playoffs.

“A lot of my friends say since the 2008 Super Bowl, they really haven’t come through in those high-pressure games,’’ said Baker, who had more faith in the defense when it was led by established tough guys like Tedy Bruschi.

Boston College historian O’Connor said he understands the collective angst of Boston fans, something he believes is ingrained into the culture. Despite the racial and ethnic diversity in the region today, O’Connor believes Boston still has a deeply Irish streak that passionately wants to win, while secretly expecting to lose.

“I wonder how many watched the game knowing that the Patriots are going to win and somehow waiting for something to happen, that one thing that would let them say ‘I knew it’ ’’ when the Patriots lost, said O’Connor, author of “The Boston Irish: A Political History.’’

Raymond L. Flynn, former mayor of Boston and a former Celtics ballboy and basketball legend at Providence College, said Boston fans should try harder to appreciate the quality of their teams rather than judge each season by whether Boston hosts a championship parade. After all, he noted, professional sports are far more competitive than in earlier generations, with more teams and more pressure, making championships more difficult to achieve.

“On any given Sunday, on any given day, anything can happen,’’ said Flynn, who served as mayor from 1984 to 1993. “It shouldn’t be just all about winning. It should be about doing the best you possibly can.’’

Yesterday, some Patriots fans were already talking about avenging the loss to the Jets next season.

“Am I going to stick with the Pats? Yeah,’’ said Sean Morrison, a 26-year-old hotel worker who was shopping at Quincy Market. “To throw away a team because they lose one game, no way, because it’s just one game.’’

But Flynn said there’s no need to wait until next football season for a Boston championship: the Red Sox begin spring training on Feb. 13.

“Put your money in the bank on this one: I’m absolutely convinced the Boston Red Sox are going to win the World Series this year,’’ he predicted.

Scott Allen can be reached at allen@globe.com; Brian R. Ballou can be reached at bballou@globe.com.