Honesty is the medicine. Kindness is how you hand it over.

Truth that somebody can actually take has two parts, and most of us only practice one. A blunt delivery lets you feel brave while the other person spends their whole attention defending themselves, so nothing you said gets in. Softening it until it means nothing fails from the other direction. The care is not decoration laid over the honest thing, it is what makes the honest thing usable.

Before you tell someone something hard, decide what you want them to be able to do with it. Say it privately, say it once, and stay in the room afterward.