Falling out of favour

Nothing hurts more than falling out of favour with someone. It just happened. There is no reason for it and all I can say is it hurts a little. One minute (was it just yesterday) you were friends and laughing and talking and then the next thing you know, you have fallen out of favour.
You didnt do anything wrong. There was a just a change of heart on the other person's side.
There is no explanation (and none sought) - there is no reason to explain the change of heart - there is just that cold exterior from that person and strangely that hurts.