Sundance 2013: Joseph Gordon-Levitt Reveals His Greatest Challenge While Making 'Don Jon's Addiction' (Video)

One might be the loneliest number, but for Joseph Gordon-Levitt, it might be a lucky number.

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The Don Jon's Addiction actor, director and writer confessed to The Hollywood Reporter that his biggest hurdle during the process came not during the shoot but while writing a script on his own.

"I see why a lot of people write with partners," Gordon-Levitt said during a visit to THR's video lounge. "I was just writing by myself. When you're alone, you have these voices in your head telling you, 'You can't do this' or "No one's gonna take you seriously.' "

In the film, Gordon-Levitt plays a Jersey Shore-type ladies man with an obsession with pornography. His character romances the likes of Scarlett Johansson and Julianne Moore, and Tony Danza plays his father.

PHOTOS: The Scene at Park City

"What I find often gets in the way of love is how people objectify each other and put expectations on each other that they've learned from different places," said Gordon-Levitt. "So the story centers on a relationship between a guy who watches too much porn and a girl who watches too many Hollywood romantic comedies, and I find that kind of thing hilarious so I wrote a comedy about it."

Amid nagging self-doubt, Gordon-Levitt got a boost during the script-writing process from his friend Rian Johnson, who directed him in last year's Looper.

"The first person that I showed the script to was Rian Johnson," Gordon-Levitt recalled. "When he said, 'I really think you have something here; this is good,' that was probably the turning point where it got a little easier. There was still tons of hard work to do, but the long, lonely journey was the writing part because you do it alone."

Don Jon's Addiction premiered Jan. 18 at the fest, and while most actors and filmmakers are in and out of Park City within days of their premiere, Gordon-Levitt will stick around till the bitter end, when he will serve as host of the festival's awards ceremony.

Email: Sophie.Schillaci@THR.com; Twitter: @SophieSchillaci