Preparation really is the key. I had no issues going in my first time and I'm not even that good of a pilot, I'm just a Boy Scout following the motto to be prepared. To quote a book from a different hobby: Relax, don't worry, and have a homebrew.
The entire experience is a ton of fun, even when things go sideways. My friends in their Bonanza and I were trying to get in for our first time on Sunday in 2018, which was reportedly among the worst times in history. All the Saturday mass arrivals got pushed back to Sunday and they were using 9 or 27 for those and 36L/36R for the rest of us, forcing a full mile spacing and a lot of shenanigans. But despite that, when we diverted out of the hold for lunch at KDLL the landing order was my friends' Bonanza, then Patty Wagstaff, then my Arrow. We had some entertainment there, including watching someone whose new Twin Beech just didn't want to keep the oil in both engines all the way to Oshkosh and listening to the Fisk frequency on the FBO's loudspeaker. After lunch, we held at Green Lake a while longer and finally gave up, ending up at KUNU, where we and maybe a couple hundred other planes set up camp for the night. Two planes down from us, we found the former owner of my friends' Bonanza. They had a guitar and everyone had booze, so it was a fun airplane camping experience even if it was a few miles south of where we had planned to be. I think you have to bring your own champagne if you're in a Cirrus, but other than that you will fit right in anywhere between the arrival and the air show.
When I finally got in through the mess on Monday morning, I thought I was home free but I got told to sidestep from 36L to 36R as I was turning final. The reason became clear as I touched down on the red square: The Trimotor took off from 36L and swooped over me as it turned out toward the lake. That was my "Welcome to Oshkosh" moment and I'll never forget it.
Back to preparation... Know your power setting for 90 knots in different flap configurations so you can spend less time inside the cockpit chasing the ASI needle. Practice spot landings a little bit. And then just fly the thing, don't bend your airplane or cook your cylinders in the name of doing something just right. For example, people have bent their airplanes trying to land exactly on their dot. It's far better to miss the dot by a couple hundred feet than to foul the runway in front of thousands of spectators. Because the rest of POA will all get there before you and set up our lawn chairs and beer coolers to watch you land.
TLDR: Don't stress out. It's supposed to be fun and it will be fun.