A source tells ET that the actor feels "incredibly relieved" to take some time to rebuild "lost moments" with his six kids -- 14-year-old Pax, 13-year-old Zahara, 12-year-old Shiloh and 9-year-old twins Knox and Vivienne -- whom he shares with ex Angelina Jolie.

"He spent over a year learning to live a healthier lifestyle and he feels better than ever," the source says. "He is more than ready to take on a much larger role in his children's lives and that is finally happening. He missed being with them on a daily basis and this last Father’s Day with them was incredibly meaningful."

Earlier this month, Jolie was ordered by a judge to help repair her children's relationship with their father. According to court documents, a judge determined that the kids "not having a relationship with their father is harmful to them." In addition, the judge determined that it is "critical that each of them have a healthy and strong relationship" with both Jolie and Pitt.

"The judge's ruling to allow him to finally be with his kids for an extended time, without Angelina's involvement, has changed Brad’s life," the source claims. "He is incredibly busy with each of them and he wouldn't change that for anything. He has planned to take his kids to do a little sightseeing, visit museums and to enjoy England’s summer weather. The kids are his first priority at the moment."

As for his dating life, the source says Pitt has "chosen fatherhood over dating."

"Brad was taking time to date, when he had the time. He also enjoyed quietly dating," the source says. "But now all he wants to do is focus on family. He has taken a step away from dating because of the importance of his children and also to help mend fences with Angelina."

"[He and Angelina] still don't get along at all, and in fact, they can barely be in the same room," the source claims. "Brad doesn't want to rock the boat [by dating]. He wants to try to co-parent and the last thing he needs right now is to start another war because things seem smoother than they've ever been."