MENTAL HEALTH. This poor guy can't catch a fvcking break when it comes to traumatic or near-death experiences. Whoever told you being a vampire is "fun" was lying through their fvcking teeth, just so you know. Between the night of his parents' death, nearly dying from the attack of the psi-hounds, and those few days he spent captive in Spokane with Rose and the others... Christian has a fair bit of PTSD. He's also got mild depression. He takes medication for it. Other than that, he's doing pretty okay.
ANGER. It honestly takes a lot for Christian to truly become angry. He's very sensitive (in touch with his feelings) and he doesn't really like to brood on things. Small things that don't matter in the long run, he lets go. But being lied to? (He hates being lied to, more than anything.) Treating other people like sh!t just for fun? Royals abusing their power to be a complete bell-end to non-royals? That stuff makes him want to immolate you on the spot. Thankfully, for you, he has self-control and doesn't do that. That being said, Christian is also a very forgiving person and if he can see through your actions that you regret whatever it is that you did, he's more open to you.
WORK. Technically Christian doesn't need to work. He's got money in the bank because of his parents' trust funds and his own. That being said, he works closely with Vasilisa and her council in trying to put forth new laws and regulations that can help their society for the better. He's something of an advisor to Lissa. When he isn't actually working with Lissa, he's training with the dhampirs (mostly Dimitri) in learning how to defend himself and others from Strigoi, when and if that ever becomes a problem at Court. He isn't going to go out on Strigoi-hunting field trips outside the wards - that is being left to the guardians. But if trouble comes knocking, he wants to be prepared and actually be of help.
STRESS. Christian is rather laidback, honestly. He tends to go with the flow. He doesn't get stressed out easily. Maybe he gets it from Dimitri, but more often times than not, Christian is a voice of reason among their social circle. He prefers to live in the present. You can't really help what's happened in the past. That's over and done with. You can only help what's happening right now.
RIDICULOUS. This one kind of develops into a longer headcanon about Christian and Rose's friendship but... Christian makes a lot of really awful jokes. I'm not talking about "too edgy for you" black humor. I'm talking bad wordplay. Puns. Especially where fire is concerned. He and Rose are the goddamn worst about it... and here's an example why.
SADNESS. Christian was kind of a melancholic little sh!t in the beginning of the series. He's always been kind of cynical of the world and a bit jaded, to be frank. But since he's befriended Rose and Lissa and the others, he's gotten a lot better and has a more positive outlook on life, now. He has more hope in the world and a little more self-esteem.