This is the first day, Missouri, of the rest of your life. Are you ready? No, nobody could be. Not for what’s coming.

Sunday is your first official day in the Southeastern Conference, the biggest and best in college sports. They don’t just win national championships; they collect them. The last six football champions. Three of the last seven men’s basketball titles. Three of the last four College World Series winners. Yeah, that baseball tournament you flipped past on TV last month. You’re an SEC team now. “Omaha” means more than the zoo and those annoying commercials. It’s a destination and a hope, and if your baseball team falls short frequently, your coach isn’t doing his job.

The stadiums are bigger. The crowds are crazier. If tailgating were an Olympic sport, they’d hold the trials in Athens, Ga., and Oxford, Miss. Thank goodness you know how to smoke a pork shoulder — better, if you ask me, than anyone in the country. Yes, even in the South, where I was born, raised and educated. Take that knowledge with you. It’ll help you fit in. They grill gator in Athens, roast boar in Starkville, and when a little hound dog trots by in Gainesville wearing Tennessee colors, they run toward him and scream obscenities.

Today is Day One. The next 364 or so will be about adjusting to an environment that, at least for a while, will seem over the top and strange. Maybe even a little intimidating.

“All the other fans — Auburn fans, Alabama fans, everybody, Tennessee, Georgia, right down the list — they’re looking at them, going, ‘What are these guys doing here?’ ” says Paul Finebaum, a radio host who has refereed SEC sports discussions for around 30 years. “Come on over here and let us indoctrinate you into the world of the SEC.”

You got yourself into this, Mizzou.

Alex Holmgren got himself into it, too. He was born 38 years ago in the Kansas City area, and he enrolled in college at Auburn. Met a nice Auburn girl while he was there.

So when the time came for Holmgren to pop the question in December 1997, there was a problem. Holmgren’s fiancé wanted a wedding late the following year. In the SEC, the only thing more sacred than a wedding is a football Saturday.

“We had friends that got married around that same time,” says Holmgren, who now lives in Atlanta. “It just kind of (ticked) you off.”

Being a nice Auburn girl, Holmgren’s fiancé understood, although her mother did not. All this for a football game? They planned delicately, aiming for the first Saturday in December. But that was the date of the SEC championship game. Auburn wasn’t supposed to be good that year — indeed, the Tigers went 3-8 in 1998 — but what if the team pulled a surprise? Life turns on a dime in the SEC. So they pushed it back a week, just to be safe, and were married Dec. 12.

God bless, good luck, and War Damn Eagle.

Years later, Holmgren received a friend’s wedding invitation. Florida was playing Auburn that weekend. Holmgren had tickets. When the RSVP came, he responded with his regrets. Yes, around here football is as important as life, because around here, life is football. If Holmgren sounds like a nut, consider that he’s more the norm than the exception — and that some fans even plan the births of their children around the SEC schedule. If there’s a surprise, pray to the heavens and Bear Bryant that the due date falls in a bye week.

Now that you know that, Mizzou, know this: You are entering their world now.

The biggest crazies are the ones who take a job coaching in the nation’s toughest league. Mike DuBose did it 15 years ago, when he took over at Alabama. He thought he was ready, too. DuBose had been an assistant coach in the NFL. How much tougher could it be?

“It’s just different,” says DuBose, who was hired in 1997, won SEC coach of the year and the conference championship in ’99, and was fired in 2000 after a 3-8 season.

Gary Pinkel is a smart man who knows how to win. Basketball coach Frank Haith showed last year that he can run with the big dogs. But DuBose says he just hopes that no coach underestimates the hurricane of the SEC. The pressure is heavier, the schedule more demanding. The football team doesn’t get two or three weeks to plan for Texas or Oklahoma. In the SEC, you can play Auburn, Arkansas, Georgia and LSU in four of five games. Think that sounds too cruel to be true? That is reality for Ole Miss this year.

Pinkel’s game-day decisions will be magnified like never before. Haith’s performances against Kentucky and Florida and Vanderbilt — all neighbors in the SEC East — will be scrutinized and used as bullet points if Mizzou fans grow restless. Big-time recruits, such as wide receiver Dorial Green-Beckham and hoops transfer Alex Oriakhi, aren’t great bounties to celebrate every few years; they’re logs to keep the machine humming.

If DuBose could go back in time, he says he’d tell his younger self to delegate less and spend as many hours as possible working on wins. Not glad-handing boosters or fundraising. Just wins. That’s the only currency with any value in this conference, and the path to being exposed or chased out of town anyway is to trust others with the big responsibilities.

You either know that going in, or you learn it the hard way.

“It’s not just a game; it’s a way of life. It’s a religion, if you will,” he says. “People are very, very adamant about it. … Whether you’re an assistant coach or whether you’re a head coach, once you step into the Southeastern Conference, you just understand that a little bit more is expected.”

The talking is finished now. Like a job interview or an election, there comes a time for the chatter to stop and the work to begin. And there’s been more than enough talk about this move, dating back more than a year.

Finebaum says Mizzou was given a “gift” football schedule, with Georgia and Alabama coming to Columbia and three home games to begin the season. But the time will ultimately come for the Tigers to hit the road and be the new kid in one of those SEC cathedrals. The first is at South Carolina, my alma mater, and the 80,250-seat Williams-Brice Stadium, which the fans pack beyond capacity whether the Gamecocks win 11 games, as they did last season, or zero, as they did in 1999.

It’ll all feel new, Mizzou, and because of the hasty push to leave the Big 12, your old rivals won’t be there to lend a hint of familiarity.

More than two decades ago, Arkansas faced the same adjustment. Athletic director Frank Broyles had politicked his way into the conference, orchestrating three years of backroom deals despite little support from the board of trustees. Broyles says now that the most difficult thing in 1991, the Razorbacks’ first season in the SEC, was the lack of rivals. Indeed, there’s a feeling of discomfort when your enemies are nearby, but in an odd way there’s a different kind of uneasiness if there are no foes on the horizon — because you don’t know where the threat is coming from. Arkansas struck first back then, targeting the schools in the states along its border.

“We were neighbors,” Broyles says. “And neighbors hate each other.”

Arkansas is Missouri’s southernmost neighbor, so the Hogs will be natural adversaries for Mizzou; the schools will be “crossover rivals,” meaning they’ll play football each year and basketball twice each year, despite being in different divisions. You don’t think Arkansas hoops coach Mike Anderson, who left Mizzou after the 2010-11 season, knows the stakes of those contests?

Basketball powers Kentucky and perhaps Vanderbilt should become rivals, too, because of geography and expectations. Something tells me the Gamecocks and Tigers won’t get along so well, either. Both play in a Columbia, have old contemporaries Haith and Frank Martin (who had Mizzou figured out better than anyone last season) as basketball coaches, and more than that they each have fan bases with inferiority complexes, because neither school has a national title in football or basketball.

The most interesting thing about Mizzou’s future is that it is blank. The athletic department has done what it can to improve its readiness, signing off on major renovations that’ll at least close the gap between the Tigers’ facilities and the SEC’s big boys. Haith should be expected to compete for a division title in Mizzou’s first year in the conference, even with defending national champion Kentucky on the schedule twice. The baseball team, which has produced several major-leaguers over the years, reached the NCAA Tournament this past season. And there’s growing popularity in predicting that Mizzou will surprise Georgia in the SEC football opener, and if that happens, away the Tigers could go.

The other question is how the fans will respond. Will they travel? Will they cheer like an SEC crowd?

Nothing will prepare Mizzou like the reality, though, and that reality begins today. Finebaum says he was in New York recently with a friend, and while they were walking, the friend kept looking upward, in awe of the tall buildings. Sometimes you can’t help yourself. But whether it’s in New York or Gainesville or Baton Rouge or Tuscaloosa, finding yourself overwhelmed by the grandeur is a good way to get hit by a bus.

So stand tall, Mizzou. Shoulders back, eyes forward. There might be some hazing, and there won’t be much fun in that. But you belong here.

Ready or not, welcome home.