Before Robert Downey Jr. and his wife Susan welcomed son Exton Elias on February 7, the actor was understandably nervous.

"There was all this trepidation, all this projection, all this anticipation and goodwill and a good vibe about it," he tells the May issue of Esquire. "But what you're squeezing to the side -- or what's in the glove box -- is these thousands of forms of fear. And then he was born and they've all just kind of scattered now. It seems like he's always been here."

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The Avengers actor, who wed his producer wife in 2005, realizes that "anticipation and fear" are normal parts of the parenting experience. (He and ex-wife Deborah Falconer are parents to son Indio, 18.)

"Am I going to know what to do with them? Does any new parent, even if you're not a first-time parent, ever really know what to do? Only thing you have to do, the only requirement, if you can hack it, is to not transfer your own discomfort in the moment to this fresh soul, right? You got to be mindful."

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The star, 47, adds: "I don't want to be so confident in myself. It's that balance between being relaxed enough to not be communicating anxiety and present enough to not be creating the very thing that you were anxious about by being so relaxed -- because I've seen that parenting style, too."

Though he plays Marvel Comics superhero Iron Man on the big screen, Downey Jr. wants his son to see him as "a very real human being."

"Every dad casts a shadow, you know? And that shadow is you're disappointed, you're resentful, or you feel so supported and loved you don't understand why life is so hard anyway," Downey tells Esquire. "Or, you know, it's so long and so dark that you can never step out of it, so you might as well not even try.