Call it bad timing or just back to reality, but the Standard & Poor's 500 all-time high has become a significant barrier to stock market gains.
For the fifth time in the past two weeks the broad-based index came within 5 points of its record, only to be beaten back either by technical resistance or, as was the case Monday, more disturbing global headlines.
"There's resistance to climb over a high that hasn't been breached since '07. It takes a tremendous push," said Mitchell Goldberg, president at ClientFirst Strategy.
"There's an awful lot of people out there who are just breaking even now, who have become more risk-adverse and have had enough of risk-taking in the stock market," he added. "The news cycle doesn't help."
Indeed, it was the latest out of Europe that pulled the stock market down Monday, with an agreement to bail out Cyprus banks rattling investors concerned about the deal coming apart and its contagion risk. Markets were also spooked by comments from Dutch finance minister Jeroen Dijsselbloem saying that the Cyprus bailout deal might be a template for other bank bailouts in Europe.
(Read More: Why the Cyprus Relief Rally May Be Short Lived)
Unease over the deal pulled the S&P 500 back as it climbed within 1 point of its all-time closing high of 1,565.15, set on Oct. 9, 2007.
Traders follow the S&P 500 more closely than the Dow industrials, which garners more of the public attention and has streaked to a series of nine new historic highs in the past several weeks.
"It doesn't really matter if the Dow hits a new record. It has to be the S&P 500," Goldberg said.
The S&P covers a wider swatch of corporate America than the Dow, which is seen as an economic bellwether even though it contains just 30 stocks.
Consequently, many traders still want another green light before believing the violent stock rally over the past three months is sustainable.
(Read More: Why Meredith Whitney Thinks You 'Have to be Bullish')
"Stock indices continue to suffer from the 'get no respect' syndrome as new highs for the Dow Jones and the S&P 500 are met with deep concerns about the sustainability of the advance and questions regarding any opportunity for more appreciation," Tobias M Levkovic, chief market strategist at Citigroup, said in a market analysis.
"We have become fascinated by the constant stream of rationalizations for not believing in the gains," he added.
Levkovich believes slow but steady earnings growth and the market's ability to shrug off concerns over European weakness will help keep the market on a positive keel higher.
Still, that hasn't stopped investors from worrying.
(Read More: Where's the Long Awaited Market Correction?)
"The daily grind higher in U.S. equity prices is acting like water torture for both bulls and bears," Sam Stovall, chief equity strategist at S&P Capital IQ, said in a recent report for clients. "Investors are in search of a new catalyst to trigger the next move."
Like many others in the market, Stovall has been waiting for a pullback from a seemingly unflappable 2013 rally that has seen the broad-based index swell nearly 10 percent.
Sentiment indicators have been volatile, with the most recent American Association of Individual Investors survey at 39 percent for those expecting the rally to continue. That's nearly perfectly in line with the historical average, while the bearish level of 33.3 percent is a bit higher than the norm.
But a retreat seems nowhere in sight as the market continues a fairly uneventful melt-up into rarefied air.
Bank of America Merrill Lynch attributes the market move higher to a "seller's strike" in which investors are anticipating a rollover of money from bond funds into stocks.
Even in the firms' bullishness, though, it also would like to see some kind of retreat to sustain the rally.
"The big question is, can stocks hold or extend these highs? Our asset allocation is skewed toward a view that yes, equities can extend their gains over the course of 2013," said Michael Hartnett, BofA's chief investment strategist. "But we also continue to think the probability and durability of that outcome would be improved by a healthy pullback."
The S&P 500's intraday high is 1,576.09, set on Oct. 11, 2007.
-By CNBC.com's Jeff Cox. Follow him on Twitter @JeffCoxCNBCcom.