Americans seem to be falling in love with stocks again.

Millions of people all but abandoned the market after the 2008 financial crisis, but now individual investors are pouring more money than they have in years into stock mutual funds. The flood, prompted by fading economic threats and better news on housing and jobs, has helped propel the broad market to within striking distance of its highest nominal level ever.

“You’ve got a real sea change in investor outlook,” said Andrew Wilkinson, the chief economic strategist at Miller Tabak Associates.

While the rising market may lift the nation’s collective spirits, it will not necessarily restore everyone’s portfolios. In good times and bad, many individual investors tend to buy and sell at precisely the wrong moments. They dump stocks after the market falls and buy stocks after the market rises, the opposite of what investors aim to do.

Some market experts worry that might be happening this time, too. People who got out as stocks plummeted in 2008 and early 2009 have already missed a remarkable rally. The Standard & Poor’s 500-stock index has soared 120 percent since March 2009, passing the 1,500 milestone. This year alone, the main indexes are up 5 percent. Now, the investing public seems more afraid of missing out than of misreading Wall Street again.