Ben Stiller gets extremely honest about his own shortcomings in a new documentary he produced about his parents, the late Jerry Stiller and Anne Meara.

In the forthcoming doc, “Stiller & Meara: Nothing Is Lost,” the “Severance” director speaks to his daughter, 23-year-old Ella, about a project they worked on when she was young ― and why it led to one of his most profound mistakes.

“I cut you out of ‘Secret Life of Walter Mitty,’” Ben Stiller says in conversation with Ella Stiller, referencing a 2013 movie he directed and acted in.

“It’s probably the worst decision I ever made in my life,” the actor admitted, via Entertainment Weekly.

Ella Stiller was much more forgiving than her father and told him that her scene “didn’t make sense in the movie.”

But Ben Stiller said the mistake embodied a bigger fault he sees in himself.

Actor Ben Stiller and his children Quinlin and Ella attend a ceremony honoring Stiller at TCL Chinese Theatre on Dec. 3, 2013.Actor Ben Stiller and his children Quinlin and Ella attend a ceremony honoring Stiller at TCL Chinese Theatre on Dec. 3, 2013.

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“For me, it kind of goes deeper. What it relates to is my own issues with my own obsession with my work, or ‘perfectionism,’” Ben Stiller said.

He got even more candid in an interview with The Sunday Times, in which the actor said he “probably fucked up more with my kids than my parents did with us.”

He added: “My son tells me that being a dad might not have been at the top of my list.”

“Like any parent, I remember things that weren’t happy about my childhood and go, ‘I’ll do better,’” he told the outlet. “And then I realized it was impossible to avoid making the mistakes they made. I feel like I have a really great relationship with my kids, but it’s complicated and has at times been strained.”

“When they were young, I did not get it. I thought, ‘Oh, the kids are young, I can work away and be a good dad earning for the family,’” he said. “But the bonds you form with your kids when they’re young are so important.”