Don't worry about the first rate hike—worry about this

As Federal Reserve watchers, traders and investors everywhere feverishly work to "connect the dots" regarding the central bank's next move, there may be a lot less to worry about with respect to when the first rate hike comes, than how many will follow.

No doubt the stock market will be extremely sensitive to the Fed's eventual decision to begin its "normalization" of interest-rate policy. But if history is any guide, the Fed's first rate hike is not the most worrisome.

Read MoreFive reasons the Fed should raise rates now

From the 1930s until the 1970s, Edson Beers Gould was one of Wall Street's earliest, and most successful, technical analysts. So precise were his predictions that his pronouncements were so accurate that he was followed by some of the biggest names on Wall Street for decades. He was reputed to have charged his subscribers as much as $500 a year for his newsletter as far back as 1930. His influence extended beyond the grave, according to some reports, having predicted Dow 3,000 toward the end of his life, at a time when the blue-chip average was still below 1,000 in the 1970s.

Three steps and a ... doh!
Brian Jackson | Getty Images
Three steps and a ... doh!

Equally, if not more, important were his observations about how the stock market responded to interest-rate hikes.

Read MoreMere coincidence or freaky Fed?

Gould developed a rule called "Three Steps and a Stumble," noting that stocks declined for an extended period after the Fed raised rates three consecutive times within a tightening cycle.

The first and second hikes did not do bear market damage to the stock market, but the third time was an unlucky charm.

Ned Davis Research engaged in a long-term study of Gould's rule, going back to 1919.

Between 1919 and 2000, after the third Fed rate hike, stocks were, on average, 17 percent lower eighteen months after that sell signal was generated.

We saw, again, in the last Fed tightening cycle, that the Fed's 17 consecutive rate hikes brought a very serious decline to the economic recovery and a bull market in stocks that lifted the Dow to 14,000 by October of 2007.

Read MoreWall Street expects really dovish Fed on rate hikes: survey

The damage in the last tightening cycle was the most severe we had seen since the 1930s, as we well know.

So, while Wall Street is fretting over the timing of that first rate hike, the real concern should be about the consistency of tighter policy.

The Fed is, admittedly, data dependent. And we have no way of knowing yet, if the economic data will be strong enough over the course of the next 6 to 9 months to warrant three consecutive hikes.

I remain firmly in the camp that the Fed will raise rates later, rather than sooner, and more slowly and gently, than some currently predict. In fact, given the persistent decline in commodity inflation, a weak global economy, and persistent geo-political threats, I am not certain the Fed will be raising rates in 2015, at all.

But I am watching for that third step before I worry about the stock market stumbling into a bear-market phase.

Commentary by Ron Insana, a CNBC and MSNBC contributor and the author of four books on Wall Street. He also delivers a daily podcast, "Insana Insights," and a long-form weekly version, both available on iTunes and at Follow him on Twitter @rinsana.