What is the best lesson an NCO/Officer has ever taught you?

Once I was feeling down because I was not able to make the top ranking(s) in one of the many measured categories that we were graded on - and my boat chief looked at me and said "Son, you got all the way from Momma's house through high school and college, got to the academy and (at this time) are almost going to graduate. You have made it already, just believe in yourself and keep pushing. If that's not good enough, then you have lost your own battle before it started". After that, I began to think more clearly and focus on the main goals, what was really important, and believe in my own abilities.

“Be the change you want to see as an NCO” (when o was complaining about this shotbag NCO I had as an E4, he told me if I wanted to see better NCOs I should get my SGT and be the change I want to see as a NCO)

I can't narrow it to just one. Various NCO's showed me through their ACTIONS what it means to be a SOLDIER and a person.

I reported for duty as a 2LT with the 2/30 Infantry, March 1972. I reported to the BNCO LTC Bettinger. His words were short and to the point. Lt George," make sure your people are at the proper place at the proper time and do a days work for a day's pay."

You teach people how to treat you. Even in the military, you have some control over how you’re treated.

One time in Munich Germany, around 1966, I was on a detail painting the dayroom. And while doing the painting I was doing the usual GI bitching. The NCOIC, who was also my tank commander, responded " I might not always like the job that I have to do, but I will do the best job that I can because it's MY job"

One of the best squad leaders I ever served under once told me, "You are not successful as a leader until your subordinates can do your job."

'Don'r Lie', doesn't mean open your month and tell on yourself.

I have learned great things from both sides.

Marine Corps 1974, just promoted to PFC six months out of boot camp. Message from gunnery sergeant who had been in 30 years: "For some reason known only to God and Chesty Puller, the Marine Corps has seen fit to promote you. Now, I want to tell you something about this rank that you are about to wear. Rank is about more than money, it's about more than being able to boss around those beneath you, or using it to get out of shit details, or being first in the chow line. Rank is about responsibility. As a PFC you might find yourself in charge of a fire team, a squad, or, like me on Iwo Jima, a platoon, or what was left of it. But whatever situation is thrust upon you, you have a responsibility to those who fall under your command to do what is right. If your people are hungry and they need to eat, they eat first. If they're thirsty and need water, they drink first. You take care of your people.
Always do what is best for the unit. The unit comes first. If what is best for the unit happens to benefit the individual, that's icing on the cake for the individual. And don't ever lie to your people. If you lie to those who serve under you they will never respect you, and they will do everything in their power to undermine you. If you don't know the answer to something, tell them you don't know and go find the answer. If you know the answer but can't tell them, say so. If you have to give them bad news, don't bullshit and don't sugarcoat it. They're Marines, they can handle it, just give it to them straight and let them sort it out. You keep those principles in mind and you'll do alright."
Semper Fi, gunny, wherever you are today.