ELI5- Why can’t an individual remain constantly in a state of euphoria or high? Why does everything eventually return to normal?

Question

I just had this random thought while lying on my roof, listening to “Young Dumb & Broke,” and being in that same state.

In: Other

Answer 1

You can be in a perpetual state of euphoria. Babies often are.

Also, if you only ever experienced the world lit up, would you have any appreciation of the dark alternative? I like to feel happy, because I know how it feels to feels sad.