How Zac Efron Knew He Needed to Go to Rehab

— -- Last year, Zac Efron quietly checked into rehab, though he didn't specify why.

Now he's opening up a bit about the experience.

"The challenging part was never the work. That was never it," he told Bear Grylls in a clip for the show, "Running Wild with Bear Grylls." "It was sort of the in-between work."

Efron, 26, who said in April that he now attends Alcoholics Anonymous meetings, explained that as an actor, he felt pressure everywhere he went because of the constant glare of the press. Calling it a "confusing" situation, he said he needed a "social lubricant" to be social and eventually, to go anywhere at all.

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"It was getting to the point where I was caring less about the work and waiting more for the weekend," he said. "I couldn't wait to go out and sort of let loose and have fun, but then when Monday and Tuesday were difficult to get through, then I was like, 'This is bad.'"

Now sober, Efron said that he doesn't ever want to rely on an artificial substance to feel comfortable again. Now, he meditates as often as possible in an attempt to calm his mind.

"You don't realize when you're out here, when we're in it, but I haven't thought about one thing today apart from what [we're] doing," he noted of being outdoors with Grylls. "I think that's one of the most beautiful things about nature."