"The best time to invest was 20 years ago. The second best time is now."
-chinese proverb
If you are investing for the long term, it doesn't matter what the stock market does today. The biggest gains come after the biggest drops, and if people could actually know when you hit bottom so they could invest right before it goes up, they'd be billionaires. If you have a lot of money to invest and you're scared, split it up into manageable chunks and invest it weekly, or monthly, or whatever makes you sleep better. And before you start, write an investment policy statement that you can reference if the market gyrations are making you queasy. As long as you have a clear goal and an asset allocation that fits your risk tolerance, you don't need to worry about what the market does each day.