Position before submission feels like the most obvious one, for beginners not to try and muscle out of everything! Also, thinking about claiming inside position/underhooks is something i often tell new guys.

“Hide the double ended dildo”
“Make your assholes kiss”
“Fuck them in the head”
“Fuck the back of their knee”

All solid technical advice.

“Find a human or someone who resembles one”

Rolling advice.

“Face your fears” to remember not to give up your back.

"Just relax and let it happen...like in the prison showers."
"Don't bring anything to a fight you aren't willing to eat."

One of my professors favorite saying is “everybody love everybody” before he bows us out 😂

„There is no right or wrong. Either it works for You or not.“
„No one pukes on my mat!“ (every water-break during training lessons starts with this)

Things I commonly say.

Get your grip like the George Foreman Grill "Set it and forget it."

You have to get out of your own way.

No one likes a jerkoff, don't be that guy.

You have to make yourself comfortable while making your opponent uncomfortable.

Learn to be heavy even when you are on the bottom.

"The guy on the street doesn't give a shit about your little injury; go train"

I've always liked the Rickson quote "in a fight, only 1 person can be comfortable, so make sure you are comfortable"

flat on your back? Dead. On your side? you're alive.

"Keep your enemies close, keep your elbows even closer".

I was just letting you work.

So many great ones, but since it seems we are leaning toward humorous ones:

"Be like a koala...but without the chlamydia."

As we're on Beltchecker:

"A black belt is a white belt who never gave up"

but

"A belt only covers two inches of your ass. The rest you have to cover on your own." - Royce Gracie

Don't forget to say "Gracie" before your meal

Don't break your toys... too badly.

White belts are friends, Not food.

That was more of a neck crank.

On the same note:

-Let's go light!

-Hold it just a second, if you do like THIS, you will get that submission you're doing on me right now. Yeah, just like that. Good job, grasshopper!

“Just don’t get stuck there” or “just don’t let that happen.”

one day, someone is going to try and take something from you and you're gonna have to choke that mother fucker out. It's that simple.
-Ralph Gracie.

A new student ask a coach, I keep crushing my nuts when doing an armbar how do not get that to happen?
Coaches response was: "keep practicing your armbars your nuts will learn how to get out of the way"

Lion sharpens lion.

"Elbows on ribs" is the mantra I live by

This

I'm quite sure that's mixed up with the shaolin monk pronunciation of iron sharpens iron ;-P

There's always that one bledder in the gym, bleeders and white Gí don't mix!

“A straight arm is a broke arm”

"Sorry not sorry" is a defo favourite at Origin when rolling and getting people in comprimising and controlling positions.
Its generally followed by a little giggle.