"I don't want to hurt them"

This reason feels like the most creditable, so it's the hardest to question. You're not avoiding the conversation for your own sake. You're sparing them. They've got enough on their plate, and they'd be upset. It would be unkind.

Some of that is true. The conversation will probably cause them some discomfort. Nobody likes hearing that something they do is a problem for someone they care about. If kindness meant never causing anyone a moment's discomfort, the case would be closed.

But follow what silence does to them, in place of what it spares them.

It takes away their chance to put it right. Sam, told in April, could have done something in April. He might have switched to alternate Saturdays, or taken the children on Sunday mornings, or simply said thank you and meant it. You never gave him the option. For four months he was doing something that hurt you and didn't know it, and I doubt he'd have chosen that. Most people, asked whether they'd want to be told that something they were doing was hurting their partner, would say yes, and would be dismayed to learn they'd been left in the dark to protect their feelings.

It lets them walk further into trouble. This is clearest at work. A manager who can't bring themselves to tell someone that their reports aren't good enough isn't being kind. The person carries on, the problem grows, and it ends in a formal process that might never have been needed. A friend who watches you make a serious mistake and says nothing because it's awkward hasn't been much of a friend.

It changes how you treat them. You can't carry a grievance for months and be fully warm with the person it's about. They get a cooler, more guarded version of you, and they don't know why. That's a kind of hurt too. It's more diffuse than the conversation would have been, and it lasts a great deal longer.

And it guarantees that when they do hear it, they hear it in its worst form. The choice was never between hurting them and not hurting them. It was between a small, clear hurt now, delivered with care, and a larger one later, delivered in anger and with a backlog attached.

Try turning it round. Suppose a friend of yours had been quietly bothered by something you do, for half a year. Perhaps you always arrive late, or you talk over them. They said nothing. They grew a little distant, and then one day it all came out. Would you feel they'd been kind to you? Most people say they'd have wanted to know at the start. They'd have been a bit embarrassed, and then they'd have fixed it. When the secret does come out, they find the months of silence harder to forgive than the complaint.

It's worth being honest about whose discomfort is really being avoided. Some of it is theirs, but a good deal of it is yours. You don't want to watch their face fall, or to be the cause of a bad evening, or to be the person who said the awkward thing. That's entirely human, and there's no shame in it. But it means that the kindness story is doing some work for you. It turns a reluctance that's mostly about your own comfort into a virtue.

Nickola Overall and James McNulty reviewed the research on how couples communicate during conflict. One of their conclusions runs against common advice. Warm, soft, validating communication is helpful when problems are minor or can't be changed. When a serious problem needs to change, the same softness can be harmful, because the problem doesn't get addressed. In their review, being pleasant wasn't the same as being kind. Sometimes kindness means saying something the other person would rather not hear, clearly enough that they can act on it.

Tact still matters, and chapter 12 is mostly about it. Saying the thing kindly is a skill, and you should use it. My point is only that kindness is no argument for staying silent.