Robert Saleh has lost 12 games so far in his rookie season as an NFL head coach. 

He also has lost some 25 pounds. 

Such is the life of an NFL head coach — particularly the life of a head coach hired to change the wayward direction of a Jets franchise that hasn’t tasted the fruits of a single playoff game in 11 seasons. 

Saleh has done an admirable job on a number of things in his first year as a head coach. One of those things has been masking the inherent stress that comes with the job. He looks no worse for the wear than he did the day he was hired. He remains impossibly optimistic — perhaps more optimistic than any head coach in NFL history with a 4-12 record. 

“I was talking to my wife [Thursday] night [and] I think I’ve lost about 25 pounds, so I got to get that back,’’ Saleh said Friday, two days before the Jets’ season finale against the Bills in Orchard Park. “It’s been a roller coaster that we were expecting.’’ 

Saleh, as he often points out, has been a part of four previous rebuilding franchises as an assistant coach (Houston, Seattle, Jacksonville and San Francisco) before he was hired by the Jets to run his own shop. 

“You don’t really know until you’re actually in it,’’ he said of the rigors of being a first-time head coach. “When you talk to the people around, talk to you guys [reporters], talk to fans … the scars run pretty deep and you’re trying to absorb it all and you’re trying to understand it.’’ 

You have to be around these parts for a while before you truly get a grasp of just how deep the scars of the Jets’ fans run. No playoff game since the 2010 season. Not a single Super Bowl appearance since the 1969 season. Too many head coaches, general managers and failed franchise quarterbacks to count, spinning through the turnstile. 

When every new Jets coach walks in the door, he immediately bears the brunt of the coaches who failed before him. Same with the quarterback. Jets rookie Zach Wilson, for example, has nothing to do with what Sam Darnold and the quarterbacks before him were unable to accomplish, just as Saleh has nothing to do with the things Adam Gase, Todd Bowles and the coaches before them failed to do. 

Saleh’s best weapon to combat this affliction unique to the Jets is his attitude, which has never wavered during a season that has featured too many losses, too many players lost to injury and COVID-19 and too many of his own mistakes as a rookie head coach. 

“There’s a lot of confidence in this building and the direction we’re going in,’’ Saleh said. 

Saleh, highly perceptive about the environment in which he resides, then stealthily took a different tack than Giants second-year coach Joe Judge took during his 11-minute filibuster following last week’s loss at Chicago. Judge buried the previous regime for allowing a bad culture to seep into the locker room. 

“It’s not to say that there were bad people in place before,’’ Saleh said. “I think you hire the people you hire and you do the best you can and whatever happens, happens. Speaking for [general manager] Joe [Douglas] and myself, [we’re] just really excited about the foundation that we’ve been able to lay down here. 

“It has not been smooth, by any sense of the imagination, which I think we can all agree on. But I think there’s been tremendous steps with regards to learning, understand each other, understanding the fan base, understanding this organization, you guys [reporters], and really trying to build something that’s going to have longevity. 

“That’s why this game [against the Bills on Sunday], along with the offseason, is really, really exciting and it’s going to be a fun next few months.’’ 

Special teams coach Brant Boyer is working for his third Jets head coach since he was hired by the club in 2016, and he likes what he sees in Saleh. 

“I think he’s has done an outstanding job,’’ said Boyer, who was hired by Bowles, survived the two-year Gase run and was retained by Saleh. “He’s got a great message. If I was a player, I’d want to play for him. He’s positive all the time, he does a nice job reinforcing his message all the time. 

“He’s kept the ship afloat [with] his message and his positivity where a lot of people wouldn’t be able to do that.’’ 

Now, about those 25 pounds? 

“I haven’t been able to get into the weight room as much as I want to [and] I don’t eat as much as I normally would,’’ Saleh said of the rigors of the season. “It’s a little bit of everything.’’ 

Everything, of course, is what you get when sign up to coach the Jets.