It used to be that baseball and the stock market both were long-term investments.

The daily ups and downs were meant to be ignored. It was supposed to be only the big picture that mattered. Don’t over-react to results, whether wins or losses, on any given day. Stay calm and focused. Maintain an even keel. Stay the course.

Sorry, but it doesn’t work that way any more.

Not in investing. And not in baseball, in which the loyal citizens of Red Sox Nation are so heavily invested emotionally.

Day trading now is the way of the financial world. People are in and out of stocks in a matter of hours, wheeling and dealing on fractional fluctuations.

That’s also true in the sports world.

The stock of the Red Sox rises and falls, climbs and soars, dips and plunges, day-to-day.

When the opening bell rang on April 1, Boston was the bluest of blue chips. If there’d been an IPO on the Red Sox winning the American League pennant, people would have been clamoring for a piece of the action the way fans do for tickets for Yankees games at Fenway Park.

But that bubble burst quickly, and alarmingly, as the Sox started the season by losing six straight on the road — three in Texas and then three more in Cleveland.

There was an uptick when the reeling Red Sox returned home to Fenway and, despite another disappointing pitching performance from John “Run an Inning” Lackey, knocked off the hated Yankees.

See, said Red Sox fans, there was nothing wrong with Our Team that a little home cooking couldn’t cure.

After which Clay Buchholz, who won 17 games last season while posting a dazzling 2.33 ERA, got shelled for the second time this season as the Yanks won, 9-4.

That he signed a four-year, $29-million contract extension the following day was both ironic and amusing. It also made good sense.

If, that is, Buchholz pitches the way he did in 2010, and not the way he’s started out in 2011 — 0-2, with an ERA of 7.20 and five homers allowed in 10 innings.

In any case, Buchholz is a bargain compared to the big bucks Boston is shelling out for Lackey, Josh Beckett and Daisuke Matsuzaka.

Beckett? Did somebody say Beckett?

A year ago Beckett was hammered by the Yankees every time he took the mound, giving up 31 runs and 40 hits — nine of them homers — in 29 innings over five starts.

So what did he do Sunday night, when he was opposed by 21-game winner CC Sabathia?

He pitched the way he did when he went 20-7 in leading the Red Sox to their World Series triumph in 2007, blanking the Bronx Bombers on two hits through eight innings, striking out 10.

The Red Sox stock suddenly bounced higher than the left-field wall. Surely this would turn the team around, especially with the imminent arrival of the struggling Tampa Bay, decimated by departures of star players — one of whom was outfielder Carl Crawford, who signed with Boston for the tidy sum of $142 million.

Instead, the Sox’ stock nosedived precipitously as Dice-K was rocked for eight runs in just two innings of an embarrassing 16-5 rout Monday night. And when the Rays held on for a 3-2 win Tuesday night, Boston was left with the worst record in baseball at 2-9.

The Red Sox were supposed to be a steamroller this season, rolling over the overmatched opposition on their way to at least 100 wins, the A.L. pennant, and a much-anticipated matchup with the pitching-rich Phillies in the World Series.

But instead of a steamroller, this season so far has been a roller-coaster ride, filled with dramatic ups and downs — mostly the latter, which have left a sickening, queasy feeling in the stomach of Red Sox Nation.

Calmer, cooler heads say these early games are a very small sampling in a very long season. If you’ve bought into these Red Sox — and who in New England hasn’t? — then hold on.

Buy and hold. That’s the way it’s supposed to be. Just like the stock market.

Just like the stock market used to be, that is.

Now it’s all day-to-day.

Some will be tempted, based on the early returns, to sell these Red Sox short. Or dump them, the way so many investors did stocks in the wake of the housing bust.

But those timid souls missed out on the market’s rebound, and Boston fans run the same risk now.

While past performance is not a reliable indication of future results, as always is written in the prospectus, you have to believe the Boston bats will come around. The huge question mark hanging over this season is the starting pitching.

The daily ups and downs of the market can drive you crazy. So, too, with the Red Sox.

But in the sports world — unlike the financial world — that’s what makes it so much fun, isn’t it?