The S&P 500's 1.5 percent fall Monday was the third-worst performance on the first trading day of the year since 1980. There's been only five opening days since then when the S&P was down more than 1.1 percent on the first trading day: 1983, 1985, 1991, 2001, and 2008, according to our partners at Kensho.
But the hangover doesn't last. One month later, markets have been positive 80 percent of the time (four of five times), with the Nasdaq 8.1 percent on averages, and the S&P up 3.7 percent on average.
Overall, the rest of the year tends to be positive as well, with the Nasdaq up 3 percent, and the S&P 500 up fractionally.
However, if you remove the disastrous year of 2008 the results change dramatically, with markets up 75 percent of the time, the Nasdaq is up 18.2 percent on average, the S&P up 12.9 percent.
Bottom line: Market hangovers haven't lasted if we look at past performance.
Disclosure: CNBC's parent NBCUniversal is a minority investor in Kensho.