"It was very hard for her to break up with Ben, but in the end she knew he wasn't getting better and that it was time for her to step aside," says a source of Lindsay Shookus and Ben Affleck
Lindsay Shookus, Ben Affleck
Credit: Eric Jamison/Invision/AP

After going public with their relationship a year ago, Ben Affleck and Lindsay Shookus split earlier this month after the Saturday Night Live producer could no longer handle his struggles with addiction, a source says.

“Lindsay had been supporting Ben’s sobriety and going to meetings with him. She had him in meditation and they were doing it together,” a source close to the former couple tells PEOPLE. “His recovery was something that was very important to both of them.”

As Affleck, 46, began to spiral in recent months, however, Shookus, 38, felt increasingly helpless, says the source. In the end, she decided it would be in Affleck’s best interest to end the relationship.

“It was very hard for her to break up with Ben, but she knew he wasn’t getting better and that it was time for her to step aside,” says the source. “She was trying to stay as close to him as possible so that he would stay on the right path, but ultimately it just wasn’t possible. She knew she had to let him hit bottom.”

Adds the source: “All she wanted was for him to be happy and healthy. It was a difficult choice but the right one.”

An Affleck pal previously told PEOPLE the couple called it quits because of distance and timing, adding that the split was “amicable.”

Affleck — who was seen recently spending time with 22-year-old Playboy model Shauna Sexton — entered rehab on Wednesday. His ex, Jennifer Garner, 46, drove him to a Malibu treatment center.

An insider told PEOPLE he “knew he needed help and was vocal about it.”

Affleck — who shares daughters Violet, 12, Seraphina, 9, and son Samuel, 6, with Garner — first sought treatment in 2001 when his pal Charlie Sheen drove him to a facility where Affleck completed a 30-day residential rehabilitation program.

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In March 2017, Affleck revealed in a Facebook post that he had again completed treatment for alcohol addiction. “I want to live life to the fullest and be the best father I can be. I want my kids to know there is no shame in getting help when you need it, and to be a source of strength for anyone out there who needs help but is afraid to take the first step,” wrote the star.

If you or someone you know is in need of help, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.