9 p.m. and still crying

9 p.m. is for our standards not so bad actually. Dear daughters are allergic to sleeping. But why is F crying this time, that is the question. She started crying like she was in panic. What is it? Do you have pain, did you get scared? What happened? She has music on when she goes to sleep, this a solution we found for her being scared after the lights go off. It worked quite well till now. Sobbing she says to me: 'this is such a nice song, this is so nice' -more sobbing-. Of course, why not? If you like a song - even if you hear it 1000th time - you cry. There is always a reason to cry! What should I do, laugh or cry?