Unless you've been under a rock, you know that Bradley Cooper is coming off a big year—a career-altering, mind-blowingly big year. It's his time. But the 38-year-old Oscar nominee, who's following an acclaimed turn in The Place Beyond the Pines with The Hangover Part III, knows that what he does next will ultimately define his place in Hollywood. Cooper sat for a candid conversation with Details' editor-in-chief and opened up about the perils of playing assholes, wanting to be a ninja, and why the 2011 Sexiest Man Alive is living with his mom. Got a problem with that?

DETAILS: You've just wrapped up a whirlwind awards season for Silver Linings Playbook. Do any highlights stand out to you?

Bradley Cooper: The whole thing was an amazing experience. Going to the White House to meet with Joe Biden was definitely memorable. He's a master. Comes in the room and comes right up to you. To everyone. He doesn't give you a second to be insecure. He turns your brain right off and makes you feel completely at ease. We screened the movie at Walter Reed the same day. Meeting with patients there. Wow. That was incredible. That was the same week Chris Kyle was murdered by a vet who apparently had PTSD.

DETAILS: You had already optioned the rights to the book Kyle wrote, American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History. Did you have a chance to meet him?

Bradley Cooper: I only talked to him on the phone. And I've since corresponded with his wife. The whole thing is just awful. I mean, two young kids.

DETAILS: You've said you loved soldiers growing up.

Bradley Cooper: I was obsessed with soldiers, wanting to be a soldier. Being a kid, I was scared of dying. Didn't feel like anxiety, I just wanted to get to a state of comprehension about death. I wanted, in a visceral way, to comprehend mortality. I was young, maybe 7 or 8. I would constantly ask my father about God and existence. And then he was simultaneously showing me these movies. Movies like Apocalypse Now and then Platoon. For some reason, those stuck with me. All those characters seemed to know something. And I wanted to know that. I figured the only way to understand life was to have been through something like these soldiers had been through. I became obsessed and started to read all these books about Vietnam. I remember this one book called Guns Up! that blew me away.

DETAILS: Did you ever seriously consider enlisting?

Bradley Cooper: Yes. So I begged my father to send me to Valley Forge Military Academy. I found the number in the Yellow Pages. He said no. I said, "Dad, I want to go." And he said, "You don't know what you're talking about." Before that, I thought only ninjas understood the meaning of life and death. And so I begged my father to send me to Japan until I was 21, so I could train to become a ninja.

DETAILS: I have to ask: Did you have a lonely childhood?

Bradley Cooper: No, but I was sort of isolated. I would definitely have a lot of time alone—but I was always around people. Much like my life now: alone, but around people.

During the filming of Hangover 2 in Thailand, I used to envy Zach [Galifianakis], because he would go on these long walks all the time by himself. I remember thinking, "I want to do that." I don't really do that very well . . . like, just go chill by myself. Or go eat dinner by myself. I wanted to just be okay being on my own. And I wasn't. I don't know what's happened, maybe the death of my father or that I'm getting older, but I realize that I enjoy it tremendously now . . . being alone. I can stay alone for days. And be okay. I never thought that would happen. But I love being alone now. I was just alone for seven days in Paris. I needed to decompress after all the running-around we did with the second life that Silver Linings Playbook had. So in Paris, I did nothing. Slept till noon every day. Walked around. I was just by myself, riding my motorcycle at two in the morning when the city was completely empty.

DETAILS: So you somehow managed to find a sense of calm in the middle of what was probably the busiest year of your life?

Bradley Cooper: I exhale a lot. I was thinking about this yesterday. My mind is pretty clear. My mind has been pretty clear for a long time. My father's death had this impact on me. It's like I was saying about when I wanted to be a soldier. I think my father's death addressed some of the fears or quandaries I had as a child about mortality. It was his parting gift to me. Watching this man—my father—leave his body and go. Watching him die. All of a sudden I was like, "Oh, right, I'm going to die too." Here it is. It's not in a book. It's not in a movie. It's not in a story that was told to me. It's not driving by an accident or watching it on TV. It's someone you love dying in front of you. I was like, "Okay. This is death. And this is going to happen to me one day." There was a huge freedom that came with that. So now I just don't sweat the shit. The small stuff. My mind is just less busy now. There were so many times when I would sweat the small stuff. All through my life. High school. College. As an actor. My dad's death allowed me to be more at ease with being myself. And if someone's not going to like me, that's just the way it is. I used to think, "Oh, my God. I don't want to make anyone not like me. I don't want to ruffle any feathers." Now it's like, "I'm just going to be myself and trust that." And I'm enjoying life more.

DETAILS: Did your dad's death make you more religious?

Bradley Cooper: I grew up Roman Catholic. I was baptized. I always loved the pageantry of it. A lot of it had to do with loving my father and looking at him wear his tweed blazer to Mass. I loved the way he prayed, so I would pray like he would. Not for any other reason than I wanted to be like my father—I wanted to be like Charlie Cooper. But in so doing, through the ritual of it, I started to have faith in God. Am I a spiritual person today? Yes. I don't know how I could not be. It's like saying, "Do you breathe?"