Wall Street traders have a unique challenge in placing bets on the stock market now that the Federal Reserve has started cutting interest rates: History is no longer a guide.

A record-setting week for Wall Street is closing on a quieter note Friday, and U.S. stocks are pulling back from their highs hit during a worldwide rally the day before. The S&P 500 was down 0.5% in late trading,

"From a sentiment perspective, we're one bad macro data point away from a pullback," BMO's Brian Belski told Business Insider.