Pete Alonso is always radiating positivity.

It doesn’t matter that the Mets are coming off a rough road trip out West, in which they lost five of seven games against the Dodgers and Giants. It doesn’t matter that the team had plummeted to seven games behind the first-place Braves in the NL East as play began Monday. It doesn’t matter if the offense has made headlines for all the wrong reasons.

What does matter, according to Alonso, is that the Mets maintain their belief.

“If you don’t believe in yourself, then who else is going to believe?” Alonso told The Post on Monday at a 9/11 Memorial Museum event. “And I think that for us, the belief has never gone away and we always believe in ourselves, regardless of the outcomes, regardless of the standings. I know that we have a bunch of high-character guys in our clubhouse, and if you work hard, we got talent, only good things are going to happen as a result.”

While the Mets collected just two wins in their past 10 games, Alonso pointed out there were plenty of close games in which things came down to one swing or one pitch. And with Javier Baez, who drove in a run and scored another in the Mets’ 7-2 win over the Dodgers on Sunday, back in the lineup, in addition to Francisco Lindor’s imminent return, Alonso is confident the team will see an offensive boost.

He said the key to capitalizing on the upcoming 10-game homestand, in which the Mets will face the Giants, Nationals and Marlins, will be timely hitting, quality pitching and good defense.

“We definitely could be better,” he said of the offense. “But I think that our process is excellent. The game of baseball is a very tumultuous game, it’s a marathon, it’s not a sprint. I feel like when we come down this home stretch it’s going to be very fun time.

“We’re never out of it, we’re never out of it.”

Even with baseball on the top of his mind, Alonso had been looking forward to coming to the 9/11 Memorial Museum on Monday for the unveiling of artist Charles Fazzino’s artwork memorializing the 20th anniversary of the terrorist attacks.

The event also featured Yankees legend Bernie Williams, who regularly visited Ground Zero and comforted families after the attacks, former Mets COO Jeff Wilpon, who is on the Memorial’s board of trustees, former NYPD Chief of Department Joseph Esposito and former FDNY commissioner Salvatore Cassano.

Alonso has been at the forefront of the New York City charity scene since his rookie season in 2019, when he famously ordered custom cleats — without MLB’s approval — for each of his teammates that commemorated 9/11. He also donated $50,000 of his Home Run Derby winnings to the Wounded Warriors Project.

The way Alonso’s face lights up while discussing his charity work, it’s easy to see how much the 26-year-old truly enjoys it. He made a point to commend New York City for its resiliency, not only post-9/11 but amid the relentless battle with the coronavirus pandemic.

“There’s tough times going on,” Alonso said. “But to be doing an event like this, especially for the 20th anniversary, it’s all about resiliency, resiliency and hope. To be able to be a part of this is really special.”