Reveler’s remorse struck investors – again – as the New Year dawned.

The stock market rolled into both this year and last near at an all-time high only to stumble from the start of January, putting a broadly optimistic Wall Street on edge.

As noted here Dec. 30, as the market hit its all-time high, the end of 2014 was a virtual replay of 2013.

The echoes have continued. As in January 2014, so-so U.S. growth data, financial upheaval abroad and doubts over the continued resilience of corporate profits undercut widely shared expectations of more market gains and an accelerating U.S. economy that would finally allow interest rates to rise toward “normal levels.”

We’re even getting another blast of crippling winter weather now, a year after the “polar vortex” took some blame for stalling economic progress for a few months.

A year ago, the market setback measured almost 6% and lasted until Feb. 3, at which point stocks’ long upward march resumed until late summer. Beginning at its Dec. 30, 2014, peak, the Standard & Poor’s 500 index retreated by as much as 4.9% before nearly pulling even for the year last week.

So, have the January jitters – 2015 edition – just about run their course?

Parallels to last year

Many indicators of investor mood and equity-market fundamentals since then are certainly tracking closely with last year’s path, arguing tentatively that markets are moving past a minor bout of panic.

The CBOE S&P 500 Volatility Index in both years went from a December low near 12 – a level suggesting that traders were expecting calm – to above 20 in January, before settling back into the mid-teens where it now sits.

On the surface, this has the look of a passing storm that did little damage. But the jumpier action in all asset classes and the preponderance of 1% daily moves in big U.S. stock indexes hint that the character of the market has subtly changed and we might be in for a less gentle ride in 2015 even if stocks should strengthen further.

The whippy action in stocks and unconvincing evidence of global growth have helpfully dimmed overoptimistic market expectations among investors.

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Both last year and so far in 2015, the sentiment split in the weekly American Association of Individual Investors poll went from frothy (over 50% bulls and fewer than 20% bears) to a more neutral reading with bulls just below the historical average of 38%.

The market “conversation” has also followed a familiar script this year. Last year began with a general agreement that the Federal Reserve would methodically wind down its quantitative easing stimulus plan – only to have the alarming drop in first-quarter GDP raise doubts about this and spur a furious rally in Treasury bonds.

Entering this year, the market figured the Fed would first lift short-term rates in the summer as growth quickened and labor market tightened. But softer world economic performance, the oil swoon, widespread deflationary concerns and the absence of U.S. wage gains have already pushed the expected first rate hike into December and helped push 10-year Treasury yields below 2%.

Equity valuations today look almost exactly as they did a year ago. The S&P 500 is priced at 19.3-times the past 12 months reported earnings; the same week in 2014, that multiple was 19. Stocks’ multiple on forecast profits for the coming year is also where it was then, near 16.

It's different this year

But here is a possible divergence between 2015 and 2014: The earnings cycle is more mature and is starting to appear more fragile this year. Energy-company earnings will be down some 25% for the fourth quarter, bank earnings were broadly disappointing and so far this earnings season companies are beating estimates at a lower rate than usual.

Bank of America Merrill Lynch notes, too, that downward revisions of profit expectations have been most prominent in consumer discretionary stocks – a consensus favorite entering 2015.

The strong dollar, too, appears not to have been sufficiently built into analysts’ forecasts, and could be a source of shortfalls in reported results by multinationals.

Of course, Corporate America’s capacity to bolster its lush profit margins has been prematurely denigrated for years. This week is the heaviest reporting week of the quarter, with a chance for tech leaders such as Apple Inc. (AAPL) and Microsoft Corp. (MSFT) to alter the narrative.

The S&P 500’s dividend yield as of Friday’s close was 2.02%, barely distinguishable from the 2.07% one year earlier.

What has changed is that risk-free rates have collapsed in the past year, with longer-term government bond yields near zero in parts of Europe and the 10-year U.S. Treasury yield around 1.8%.

This arrangement, with dividend yields exceeded Treasury rates, continues to stoke demand for stocks among income seekers and deflationists, even as growth optimists and value seekers have wavered.

Morgan Stanley strategist Adam Parker notes that some 75% of all U.S. stocks pay a dividend, the highest percentage in more than 20 years, as corporate executives share cash as a selling point for their shares in an income-parched world.

And so, we still have yield-centric sectors such as utilities, consumer staples and healthcare holding up the broad indexes, forestalling expectations that a new market “story” animated by domestic consumer strength was about to start.

All well and good, but the ballast of a dividend can only do so much; investors who bought the SPDR S&P 500 fund (SPY) for its 2% yield on Dec. 30 lost twice that on paper within a couple of weeks.

Perhaps the most unsettling aspect of the current market, even as it has stabilized impressively, is the way powerful and vagarious winds from other asset markets continue to whip around it. Rapid currency swings, oil and iron ore price crashes and global equity-market whipsaws make some traders tremulous.

As Michael Block, strategist at institutional broker Rhino Trading, put it in a client note Monday: “I still maintain that [currency], commodity and stock moves like this are ‘perturbations’ that signal that something is wrong, but given that the central bank ‘put’ is in place, it’s hard to fight.”

We'll see before too long whether these conditions begin to make 2015 look a bit different from the market we’ve become used to.