Missing a few strong days hurts more than missing many average days. For a long-term investor, the missed opportunity from being out of the market during the 10 best days is far greater than the risk of being in the market during the 10 worst days. For example, one analysis found that over 20 years, missing the 10 best days could reduce returns by 50%.
Timing the market is nearly impossible. Successfully navigating market volatility would require an investor to make two perfect decisions: when to sell to avoid a downturn and when to buy back in to capture the rebound. This is practically impossible for both individual and professional investors.