Here‘s a number you’ve probably heard: the S&P 500 has historically returned about 10% per year on average.

Sounds steady and reliable. But here‘s the number nobody talks about: miss just 50 of the best trading days over 40 years, and your return drops to zero. Not a little less. Zero. You’d have been better off keeping your money under your mattress.

Let me show you why staying invested matters more than anything else — and why trying to time the market is a trap.

The Math That Should Keep You Up at Night

A $10,000 investment in the S&P 500 on December 31, 1985, would have grown to about $75,000 by the end of 2025.

Now watch what happens when you try to be “smart” about it.

Days Missed	Final Value of $10,000
Fully invested	$75,242
Miss top 10 days	$33,473
Miss top 20 days	$19,443
Miss top 30 days	$12,358
Miss top 50 days	$5,607

Source: Robertson Stephens analysis

Missing just 10 days cuts your return by more than half. Miss 50 days, and you‘ve lost money during a period when the market boomed.

That’s not bad luck. That‘s the math of market timing.

The Specific Days That Changed Everything

Here are some of the S&P 500’s best trading days of the past 25 years:

Date	Return	What Was Happening
Oct 13, 2008	+11.6%	Financial crisis peak — Banks were failing. Panic everywhere.
Oct 28, 2008	+10.8%	Financial crisis — Just 11 days after a -8.8% crash.
March 24, 2020	+9.4%	Pandemic — The day the CARES Act was announced.
March 13, 2020	+9.3%	Pandemic — Right in the middle of the worst selloff since 2008.
April 9, 2025	—	Tariff selloff recovery — The best single day of 2025.

Look at these dates. Do you see the pattern?

Every single one happened during a terrifying economic moment. The financial crisis. The pandemic. Trade wars. The market‘s best days don’t happen when the news is good. They happen when fear is at its peak.

And here‘s the kicker: seven of the ten best trading days of the past three decades came within just one week of one of the ten worst days.

If you sell to avoid the bad days, you will almost certainly miss the good days that follow immediately after. You can’t have one without the other.

Why Investors Keep Falling Into This Trap

The best trading days don‘t happen in calm, predictable markets. They happen during chaos.

Think about March 2020. The S&P 500 fell nearly 30% in weeks. Anyone who sold “to protect their gains” locked in those losses. But anyone who stayed invested captured one of the strongest bull markets in history starting later that month.

The same pattern showed up in 2025. The S&P 500 fell nearly 19% in the spring. Right in the middle of that volatility — on April 9, 2025 — the market posted its strongest single-day gain of the entire year. Missing just that one day would have cut your annual return by more than half.

This is what market timers never understand: the best days and worst days travel together.

According to Vanguard, ten of the 20 best trading days occurred in years with negative total returns. The market‘s greatest single-day gains often happen during years when the market overall went down.

What Actually Works

So what should you do instead of trying to time the market?

Stay invested. That’s it. That‘s the strategy that has worked for decades.

The investors who built real wealth didn’t do it by jumping in and out. They did it by buying consistently — through bull markets and bear markets — and never selling until they needed the money.

If you‘re investing for retirement that’s 20 or 30 years away, short-term volatility doesn‘t matter. What matters is that you’re in the market when the best days happen.

A second strategy: keep buying during downturns. The investors who made the most money in the 2009-2020 bull run weren‘t the ones who sold in 2008. They were the ones who kept buying when prices were low. It’s emotionally difficult — buying when everyone else is selling — but the math is undeniable.

The S&P 500 Averaged 10% Over 40 Years. Miss the 50 Best Days, and Your Return Drops to Zero.