And can you really blame them for worrying? After all, it's been 14 months since the S&P 500 has seen a 5% selloff, and 19 months since a full-blown 10% correction.
Still, Goldman says fear not, for there are still a couple key factors working in the favor of a prolonged stock market expansion.
The first is a lack of investor euphoria - the type of unabashed confidence that has historically left past bull markets vulnerable to sharp downturns. Goldman cites cash positions of 3.2% for mutual funds, which is in line with the historical average. If there was an overabundance of confidence, this measure would be far lower, with more capital in play.
"Investors today are situated between skepticism and optimism," a group of Goldman strategists led by David Kostin wrote in a client note. "Few are euphoric as 27% of core managers are beating their benchmark. 'Tormented bulls' best describes investor mentality."
A second factor that should keep the stock market afloat is persistent US economic expansion, says Goldman. The firm specifically cites strong monthly job growth, rising wages, confidence at its highest level since 2001 and household balance sheets that are the strongest since 1980.
Goldman Sachs
Household balance sheets are the strongest since 1980, one of several factors supporting a continued stock market rally.
Further, both sales and earnings growth for US corporations are headed for more growth in 2018, while companies clearly don't view their shares as overvalued, as indicated by their continued willingness to repurchase their own shares, says Goldman.
Overall, the firm argues that investors would be wise to keep these positive drivers in mind as they watch the stock bull market continue into its ninth year. Instead of worrying about the rally dying of old age, traders should be focused on actual fundamental drivers.