[@Antarctic Termite] How about this:

Hmm, how about: being nihilistic and superintelligent is all good, but combined they drive you into a mega-existenial crisis meaning that you just end up moping around on the ground doing nothing 'cause it's all so f**king pointless. so pointless. 

So you're in the odd position where your hormones or whatever are exploding and giving you positive feelings, but your newly acquired nihilism and intelligence makes you super-depressed. Conflicting feelings are so intense that they can lead to various psychological conditions, amongst them: permanent personality change (it's an actual thing, I read about it in one case...), schizophrenia, PTSD (and anything else that can develop from severe psychological shock)