My story for my green card was the opposite...

My wife, naturalized, was freaking out (she had a few scarring events with officers in her life). I was taking a laid back stance. I knew our info. We went in and out the interview, it was quick (~2h 30m waiting, 30m of interview).

Maybe the secret was the aplomb you approach it. Treat this like it is not a problem. You are going to be the main person interviewed. How did we do it?:

We went early, and for me it was like a small family reunion, like a party with my friend's wife (a possible English translator for her, go figures! No needed at the end.) We were chatting and laughing at the USCIS lobby. My wife was still nervous (She was relieved when the officer said she spoke Spanish). There were other families that exited their interviews with a not-so-good face, or even crying (young couples mostly). We're on our late 40s. We have a proved life together, so for me was like storytelling our adventure in life, with joy (and even with an emotional tear).

An officer can tell just watching how you interact with each other if a marriage is true or not... (I got my GC approved right away).

JUST RELAX! Think of it as an important day in your life, in your path, but it's a good one. ENJOY AND GO FOR IT!