In Happiness Hypothesis Jonathan Haidt talks about how we all have a basic setting for these kind of things.

We can move the bar around but it always tends back toward that default.

He uses the example of this being why people who read self help book always seem to be reading a new self help book.

That little euphoric moment of clarity and fresh outlook only last a few months or so until you’re back at your regular old self and need a new epiphany.