Megan McArdle, who has recently been obsessing about what government can do about obesity (A silly obsession, in my view. Why has it become a reflex for people to ask "What can govt do?" about this or that thing, as if government had magical powers to alter reality?), used the Swedish word "lagom" in a piece about Ikea.
The word is not easily translatable into English, because it is such a dispirited, dysthymic Swedish concept.
Want to give it a try?