I think what TV IWTV did really well is asking the question: what is humanity? Anne Rice tried to do this in all her writings, but sometimes it got too complicated and lost in her elaborating writing. The TV series simplified it but was much more to the point (and true to the TV medium).
As human nature, you usually don't miss something until you've lost it. So after everyone has been turned to a vampire and lost their humanity, they began to try to regain it. Louis's way was ruminating, lost in the sorrow of mourning it so much so that he forgot he was still kinda living and had the possibility to be happy ever again.
Lestat imitates humanity by being something larger than life, something shiny and desirable by all; despite what he really felt inside, he performs all the time and is not living it honestly neither.
Interestingly Armand is also performing all the time. Maybe the longer you lived the further you distanced from humanity. He portrays himself as he imagined other people want to see, need him to be. I think he no longer has much of an idea of what humanity is after five hundred years of living. The difference is Lestat is rebellious, he fights back against people's view of him and Armand molded himself against people's demand out of fear of abandonment.
And last, Daniel, who had a longer life than any of them and by far the most human of them all. I think he wanted vampirism when he's young and didn’t know any better. But now he got it and he hates it, doesn't want it. But admitting this will also prove Armand was right to erase his memory so he can't admit it. That's why he's acting so flamboyant, so crude, like he's having the best time of his life, but inside he actually feels fear and disgust of the thing he became and he's not at all okay with killing people every night so he can survive. He's a reporter after all, he wouldn't be doing that if he didn't care for people. In this character lays the most struggle with humanity and the loss of it.
