“I don’t care” is usually the loudest sign that you do.

Indifference does not need announcing. When you actually do not care, the subject just passes, and you have nothing to say about it, because there is nothing there. The declaration is doing work: it is a way to be disappointed without admitting you were hoping, which protects you from looking like you wanted something you did not get.

When the phrase comes out of your mouth, treat it as a flag rather than a fact. Ask yourself what you were hoping for, and whether it is still available. Wanting something and missing it is ordinary, and pretending otherwise mostly means you cannot try again.