This is our second installment of Do This, Not That. You can read our previous article here.

No one signs up for a race thinking, “I hope this is awful!” That would be just wrong. (And kind of weird.)

That’s why you spend weeks putting in the miles to prepare. You’re proud to say you followed your workouts down to the letter. You’ve sailed through all the strides and finished every squat. You even went to bed early (gasp!) a few Friday nights so you could be well-rested for your Saturday long run.

But race day can be sabotaged in a hot minute with just a few simple mistakes. Here’s how to avoid them.

Nothing new on race day.

When we say don’t try anything new on race day, most people think shoes, a sports bra, or a major clothing item like leggings. (The chafing stories are real.) But nothing new applies to every. single. thing. you can put on—or in—your body.

Nothing new includes the purple running visor you spy at the race expo. It matches your shorts perfectly and would be so fetch for tomorrow’s half-marathon, but what you don’t know is there’s a tiny spot where the lining is just waiting to scratch your head for the entire race.

Nothing new means the pair of socks your sister swears are soft as butter, but you discover at mile 6 they keep slipping down your heels.

Nothing new is also something as innocent as a headband that winds up feeling 5% too tight after an hour. (Ask me how I know.)

From sunglasses to shoelaces, you want to know how things feel after you’ve bounced around in them for a few hours. Wear your tried-and-true favorite gear, and stock up on your favorite fuel well before the morning of your event. If you’ve completed all your long runs with strawberry-flavored chews, race day is not the time to pound down super-caffeinated espresso gels. (Insert poop emoji here.)

Dial in your pre-race nutrition.

Nothing ruins race day like your intestines starting a polka 20 minutes into your run. I’m a big believer that long training plans aren’t just beneficial for your lungs and legs, they’re also the perfect dress rehearsal for your GI system. While pit stops in the middle of a race can happen even after the best laid plans, there are some ways to minimize the likelihood of a major code brown. (See my previous emoji reference.)

There’s lots of great advice on the internet about what to eat the day before a long run or race, but my motto can be summed up in three words: bland is best. You probably want to pass on the hot sauce and beans at the buffet and steer your stomach toward easily digestable carbs like rice or pasta. Ignore the temptation for greasy fast food and focus on lean proteins.

Yes, there’s always that one friend who can eat whatever she wants the night before a race, while just the thought of that sends you running to the porta potties. We can’t explain why ice cream sundaes or nachos are the go-to meal for some runners. Even a broken clock is right twice a day, amiright?

Your superpower is to practice, practice, practice. Use those long runs to test out different options. Write down what works—the meal you ate the night before, the way you hydrated, and how you fueled on the run. The longer you train, the more you can test what food sits well in your system before a long run—and more importantly, what doesn’t.