We are taught that respect between adults looks a lot like politeness. Don't interrupt. Watch your tone. Correct gently. Don't embarrass people. If somebody screws something up, don't make them feel worse. Good friends should be supportive, considerate and kind to each other.

All reasonable advice.

And maybe a terrible diet for a friendship.

Politeness is the fast food of friendship. It is convenient, pleasant and gets us through the moment. Sometimes it is exactly what we need. But if it is all we eat, the relationship probably won't be healthy. Given enough time, it may even die.

Politeness exists for good reasons. It is one of civilization's great friction reducers. It lets strangers, coworkers, customers and people who don't particularly like each other get through the day without unnecessary collisions. It says: I am not threatening you. I recognize the appropriate distance between us. I don't know you well enough to know how you will react, so I will be careful.

That last part matters.

Politeness helps us manage people we don't know well enough to trust.

Friendship should eventually do something different.

I notice this most clearly on a boat.

Recently I was wakesurfing with three friends. Two were learning to drive with a surfer behind the boat. When each took the helm, I told him he had permission to yell at the rest of us if we screwed up.

Not ask nicely. Yell.

The driver has a human being in the water behind him. If the rope is somewhere dangerous or another boat is approaching, I don't want him worrying about tone. Responsibility gives him authority, and reality outranks politeness.

A little later, while I was driving, we proved the point.

The crew let the surf rope get under the boat. It wrapped around the propeller and severed the handle. Two guys had to free-dive under the boat to unwind it. We didn't have a knife aboard, and for a while there was a real chance our day was over.

Nobody needed a carefully worded conversation about what had happened.

They knew.

They also felt terrible, so I didn't yell at them. That would have accomplished nothing. They were already underwater fixing their mistake. One later offered to pay for the rope even though nobody was quite sure whose fault it had been. We had a spare, got going again and moved on.

Being real isn't the same as being harsh.

Years ago, I made my own rookie mistake on a friend's boat and soaked everyone's change of clothes. I got the captain's shaking-head look and about three rounds of teasing.

I never did it again.

Nobody had to manage me. I screwed up, everybody knew it, I took some grief, learned something and the mistake disappeared.

The slot car track gives me the same feeling. It is simulated life and death at 1/72 scale. Cars fly out of their slots while the race clock keeps running. Marshals around the track rescue them and get them back into the race.

When my car comes out, my friend is suddenly responsible for my race. So I repeat "Blue lane, Blue lane." Until I am put back on.

A minute later his car flies off and I rescue him. We are competing and cooperating simultaneously. There isn't much room for social varnish because we are concentrating and have something to do together. Nobody says anything about teamwork. We are too busy doing it.

Even mahjong has a mild version of this. Someone misses an obvious move, gets teased, groans and keeps playing. The tiles provide an external reality.

These activities aren't important because everyone should buy a boat, build a slot car track or learn mahjong.

They are important because they show me what changes when friends stop managing one another.

Most of ordinary social life is padded. We soften what we mean. We praise. We qualify. We let things slide. We say “no problem” when there was, in fact, a small problem.

Usually that's useful. Not every irritation deserves a summit meeting. But sometimes “no problem” has a hidden cost.

Maybe you didn't carry your share. Maybe you were inconsiderate. Maybe you keep doing something that bothers me. I decide it isn't worth mentioning, so I absorb it. The interaction stays pleasant.

Then I do it again. Eventually I trust you a little less. I expect a little less. I stop asking you to do certain things. I avoid a subject. I become more careful around you. Nothing happened between us. That is the problem.

Politeness can preserve the interaction by spending the relationship.

Friendship requires self-repair. Your friends will disappoint you, irritate you and occasionally behave badly. If every $2 offense requires a negotiation, you will become exhausting to know. Sometimes the healthy response really is to eat the cost and move on.

The question is whether you actually moved on.

Did I let it go, or did I merely decide not to say it?

If I genuinely let it go, that's self-repair. But if I say nothing while quietly lowering my expectations or changing how I behave around you, I didn't repair anything. I just made the cost invisible.

There is another reason excessive politeness bothers me. I lived in Japan for years, and Japanese has a useful idea for this: tanin-gyōgi, behaving toward someone close as though they were an outsider. Excessive formality can actually feel distancing. If a close friend suddenly becomes strangely ceremonious with you, you don't necessarily think, How respectful and wonderful.

You think, What's up with you?

That intuition exists in American friendship too. Imagine one of your closest friends suddenly becoming exquisitely careful around you. Every joke softened. Every disagreement padded. Every request phrased delicately. Every rough edge polished off.

You might not feel respected. You might wonder where your friend went.

A hard dig can sometimes communicate more trust than a polite compliment. It can say: I know you can take this. Correction can say: I expect you to be competent. Yelling from the helm can say: I trust you enough not to manage your reaction while something important is happening.

This doesn't contradict being a gentle friend.

A gentle friend doesn't humiliate you, exploit your vulnerabilities or make the relationship feel precarious. Gentleness protects the person. Politeness protects the interaction.

Those are not the same thing.

In fact, perhaps one of the rewards of building a safe friendship is that eventually we don't have to be quite so careful with each other.

That may be one reason shared activities are so powerful. The boat needs driving. The car needs rescuing. The tile was a terrible discard. Reality gives us permission to stop performing the relationship and simply experience one another.

And each time we do, we learn something important. You can yell at me and we're fine. I can tell you that was stupid and we're fine. You can laugh at me and we're fine. I can screw up, own it, fix it, and we're fine.

Those little collisions don't necessarily draw down the relationship. Sometimes they strengthen it because they give us evidence that the relationship can take a hit.

Politeness is useful. Sometimes it is exactly the right meal.

But close friendship offers something much better than perpetual good manners.

The freedom to stop managing each other and discover that we're still friends.