Brad Pittis still one ofHollywood’s biggest stars.He earnedrave reviewsfor his role as a tough, loyal stuntman in Quentin Tarantino’sOnce Upon a Time … in Hollywood— his first film in two years.Since his 2016 split fromAngelina Jolie, the actor, 55, has “worked very hard on himself to be a better, healthier person and to be the best dad possible,” a source tells PEOPLE in this week’s issue.“These were always his priorities. That his career is going well is a happy bonus that he is thrilled about.”For more onBrad Pitt, pick up the latest issue of PEOPLE, on stands FridayThe Oscar winner’s positive lifestyle changes also included focusing on his diet and workout regimen — and the results are on full display in a shirtlessOnce Upon a Timescene reminiscent of his star-makingsix-pack momentin 1991’sThelma & Louise.He “really takes his workouts seriously,” the source says. “It’s been a whole lifestyle change. And he looks amazing.”RELATED VIDEO:Once Upon A Time … in HollywoodActorsLeonardo DicaprioAndBrad PittFormed The Bromance We Didn’t Know We NeededOn the family front, thefather of sixrecently helped celebrateShiloh’s 13th birthday, andhis oldest son Maddox, 18, will soon head tocollege in South Koreato study biochemistry. “Despite having help, Brad is a hands-on dad,” an industry insider says. “He comes from a close family, and he has continued to be a parent who is interested in the lives of his children.”John Rasimus/Barcroft Media/GettyBetweenhis latest movie’s box office success and Pitt’s personal strides, he’s “really found his happiness again,” the first source says. “He is back and very excited about life. And it’s well-deserved.”Once Upon a Time … in Hollywoodis out now.

Brad Pittis still one ofHollywood’s biggest stars.

He earnedrave reviewsfor his role as a tough, loyal stuntman in Quentin Tarantino’sOnce Upon a Time … in Hollywood— his first film in two years.

Since his 2016 split fromAngelina Jolie, the actor, 55, has “worked very hard on himself to be a better, healthier person and to be the best dad possible,” a source tells PEOPLE in this week’s issue.

“These were always his priorities. That his career is going well is a happy bonus that he is thrilled about.”

For more onBrad Pitt, pick up the latest issue of PEOPLE, on stands Friday

The Oscar winner’s positive lifestyle changes also included focusing on his diet and workout regimen — and the results are on full display in a shirtlessOnce Upon a Timescene reminiscent of his star-makingsix-pack momentin 1991’sThelma & Louise.

Thelma and Louise

He “really takes his workouts seriously,” the source says. “It’s been a whole lifestyle change. And he looks amazing.”

RELATED VIDEO:Once Upon A Time … in HollywoodActorsLeonardo DicaprioAndBrad PittFormed The Bromance We Didn’t Know We Needed

On the family front, thefather of sixrecently helped celebrateShiloh’s 13th birthday, andhis oldest son Maddox, 18, will soon head tocollege in South Koreato study biochemistry. “Despite having help, Brad is a hands-on dad,” an industry insider says. “He comes from a close family, and he has continued to be a parent who is interested in the lives of his children.”

John Rasimus/Barcroft Media/Getty

Brad Pitt

Betweenhis latest movie’s box office success and Pitt’s personal strides, he’s “really found his happiness again,” the first source says. “He is back and very excited about life. And it’s well-deserved.”

Once Upon a Time … in Hollywoodis out now.

source: people.com