低谷 (dī gǔ): valley; trough (as opposed to peaks); fig. low point; lowest ebb; nadir of one's fortunes

He got sick and lost his job last year; that was the low point of his life.

The company suffered losses for three consecutive years and fell into an unprecedented trough.

When she was in an emotional low, she often took walks alone in the park to gradually adjust her mood.

That movie tells the story of an athlete who bounced back from a low point.

During the economic downturn, many small shops closed down.