Our common understanding of mental health is a caricature

You're not always either depressed or fine. Sometimes you're just in the middle, and that's what is called languishing.

It's a state where you're just meh. You're not really suffering, but you're not exactly fired up either.

That state might lead to further mental health issues. Hence, it should be acknowledged.

The best way to counter it is to get ingrossed in something, whether it's playing a game, improving a skill or simply watching a movie.