Crazy -- other than the Great Depression, every decade returned 8+% -- the case for long-term investing stays & is amplified by when you get in. Timing the market is next to difficult & being on the sidelines could be disastrous, as seen in this Business Insider Post & JP Morgan chart from 2014:
Amplified in this Index Fund Advisors post which admonishes those who try to time the market, as "almost all big stock market gains and drops are concentrated in just a few trading days each year," and provides another $10k over 10 year chart:
