There are few people who would not be ashamed of being loved when they love no longer.

Being loved by someone you no longer love is uncomfortable, and the discomfort is mostly about yourself. Their feeling is a standing reminder of what you used to be, and every kindness from them arrives as a small bill. The usual response is to become distant or irritable, which is less cruelty than an attempt to stop being reminded. Naming it honestly is kinder than acting it out.

If you are in that position, say the true thing clearly rather than letting your behaviour say it slowly. And if you are on the other side of it, notice whether the coldness is an answer you have already been given.