Definition from Wiktionary, the free dictionary
Literally: Thirty years on the east side of the river, thirty years on the west side of the river.
三十年河東，三十年河西 (traditional, Pinyin 三十年河东，三十年河西), simplified
- Prosperity and decline never last.
- Life has its ups and downs.
- Everything in life is cyclical.
- Easy come, easy go.