If you're young and you've only seen the market go up you need to familiarize yourself with normal volatility patterns. The market can easily take a dump at any time and fail to provide a positive return for years.
...or decades: "Nikkei index hits 30,000 for first time in three decades"
https://asia.nikkei.com/Business/Markets/Nikkei-index-hits-3...
...or decades: "Nikkei index hits 30,000 for first time in three decades"
https://asia.nikkei.com/Business/Markets/Nikkei-index-hits-3...