I have noticed I feel crappy at night too? Could it be the stress of the day, and finally you are at home, and 'resting' and your mind gets time to just start focusing on all the stuff you ignore while you are at work? I don't know, just an idea.
I hate it when people use that line. (the one about being alone.) It's not helpful at all and at least in my case, makes me feel like I am worth even less and deserve to be alone!
I hope you are feeling better today?