unbridled joy and hilarity
Surely, Victor, like any human being, has a right to pursue happiness. But it is the case, that, beginning here, on every occasion when he anticipates a return to normal human pleasures he experiences instead a disastrous reversal of expectations. From this moment on his joy will never again be "unbridled," but rather, at best, what Thomas Gray, in his "Ode on a Distant Prospect of Eton College," called "fearful."
Some bold adventurers disdain
The limits of their little reign,
And unknown regions dare descry:
Still as they run they look behind,
And hear a voice in every wind,
And snatch a fearful joy. (lines 35-40)