The trading week ended one day too late for the bulls, with the S&P 500 tumbling more than a full percentage point on Friday. New short-selling allowances in China, hints of inflation in the United States, and renewals of worries about Greece’s debt debacle all got the blame. Regardless of the reason, today’s jolt was a not-so-gentle reminder that stocks aren’t impervious.

Dishing out most of Friday’s pain were American Express Company (NYSE:AXP), ServiceNow Inc (NYSE:NOW) and Time Warner Cable Inc (NYSE:TWC). Here’s why.

American Express Company (AXP)

American Express may have topped earnings estimates, but the market wasn’t impressed. Instead, AXP investors are more concerned about last quarter’s declining revenue and the hurdles the credit card company still has in front of it.

All told, American Express earned $1.48 per share in Q1 on sales of $7.95 billion. Analysts were only looking for a profit of $1.37 per share of AXP, but were also expecting revenue of $8.2 billion. Despite the 6% improvement in the company’s bottom line — up from $1.33 per share in the first quarter of 2014 — AXP stock lost more than 4% following the earnings announcement.

Despite the improved profit, CEO Kenneth Chenault knows the near future is going to be a tough, saying as part of the earnings announcement:

“We expect full year 2015 earnings will be flat to modestly down year-over-year with the headwinds we’re facing and as we ramp up investments to help offset the impact from ending our relationship with Costco in the U.S. next year.”

Time Warner Cable Inc (TWC)

Good news for those consumers who were worried the union of Time Warner Cable and Comcast Corporation (NASDAQ:CMCSA) was only going to augment the terrible customer service and unfair pricing each currently dishes out on its own — the Department of Justice’s antitrust division is reportedly planning to bar the deal. Though not yet officially stated by regulators, Bloomberg has noted the DOJ’s attorneys could recommend the agency file a lawsuit to block the Comcast-Time Warner merger.

Time Warner Cable could potentially successfully litigate the matter, as the Department of Justice’s stance isn’t a absolute legally-binding until tested in a courtroom. Investors had enough doubts about the matter, however, to send TWC shares more tumbling 5% lower on Friday.

ServiceNow Inc (NOW)

Despite the encouraging news regarding last quarter’s earnings and the full-year outlook, ServiceNow investors just couldn’t get past the company’s guidance for the current quarter, and shares took a 11% haircut as a result.

The good news: For the quarter ending in March, ServiceNow earned an operating profit of one cent per share on $212 million in sales; analysts expected ServiceNow to be breakeven on $210.7 million worth of revenue. NOW also raised the lower end of its income-range guidance for the full year, from $960 million-to-$1 billion to $970 million-to-$1 billion.

The bad news: ServiceNow “only” expects to generate revenue of between $237 million and $242 million for the second quarter of the year, up about 44% on a year-over-year basis. That growth rate is below the 50%+ growth NOW shareholders have become accustomed to.

It just goes to show: When you set the bar high, even a slight miss can be very costly.

As of this writing, James Brumley did not hold a position in any of the aforementioned securities.