Telling your parents “you were right about that” once in a while will make their whole month. It costs you nothing.

Admitting a parent got something right is free to give and unusually large to receive. A lot of the friction between generations is a long argument about whether the older person is still worth listening to, and one sentence sets that argument down for a while. It costs you nothing, because being right about one thing is not a ranking. They will carry it much longer than you expect.

Think of something they warned you about that turned out to be true, and just say so, without the qualifier you want to attach. No lesson, no follow up. Let it be the whole message.