Hillary Clinton is nothing if not prepared. And part of her preparation for the three presidential debates this year involved anticipating the actions of her “aggressive” and unpredictable opponent — and mastering her “listening woman” face.

The Democratic nominee tells PEOPLE in an interview for this week’s issue that she focused on keeping her composure during the debates, including in regard to her facial expressions. “It is something that I really was conscious of because this is the first time a woman had ever been on a debate stage in a general election,” she says.

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“It was not clear to me which Donald Trump or how many Donald Trumps would show up during the course of each debate,” Clinton continues. “So I really did have to think very consciously about how I was going to deal with whatever he said and however he behaved.”

Clinton has said that Trump tried to physically “dominate” the stage at the town-hall style debate on Oct. 9, to the point where he “literally stalk[ed] me around the stage,” she told Ellen DeGeneres in an interview last month.

Image zoom Ryan Pfluger

“That was one of the reasons I prepared so much, because you cannot just think about it, you have to go through it. If you’re in a town-hall setting and somebody is crowding your space, you need to know what that feels like,” Clinton tells PEOPLE now.

“So if it happens as it happened to me on that second debate stage, you’re not taken by surprise. Because, look, if somebody is like all of a sudden over your shoulder, it’s easy to be startled or to turn around. But I was determined to be very focused on what I wanted to say to the American people — draw a contrast with whatever Trump had to say and try to be as calm and composed as possible.”

Clinton credits her campaign staff with getting into Trump’s head and helping her shadowbox her opponent.

Image zoom Jim Wright

“I had a team of people who were relentless, totally in the head of what Trump might do,” she says. “A lot of this comes down to who gets into whose head. It’s like an athletic contest or maybe a high-stakes entertainment performance.”

“So you just have to be really aware of how your opponent — in this case, such a very aggressive and belligerent opponent — is going to try to knock you off course, play with your emotions, really game you,” she adds.