It’s that time of year. That time when we invoke the spirit of Janus.

Janus was the Roman god, the guardian of doors and gates, the god of new beginnings, as powerful as Jupiter himself. January is named for him. Janus was the custodian of the universe, and was seen as the originator and orchestrator of all things – the system of the years, the changing of the seasons, the ebbs and flows of fortune, and the civilization of the human race by means of agriculture, industry, money, and laws. Janus ensured a time of peace, honesty and abundance for his people – it was the era known as the Golden Age.

Janus particularly presided over all that is double-edged in life, and what was most unique about Janus was his two faces gazing in opposite directions. One face regarding what is behind, and the other looking toward what lies ahead. But why would the god of new beginnings be artistically depicted with one face facing backward? Answer: because doors and gates look both backward and forward, inward and outward, simultaneously. The connection between Janus and new beginnings is the idea that one must emerge through a gate or door before entering a new place.

We all adopt the manner of Janus when we are starting something new, and certainly the January turn of the calendar marks a new beginning. Yet we reflect  on the previous year even as we usher in the new. We look forward with anticipation toward the future while we look backward to the past that has led us so far and in fact has brought us to the new beginning.

The art of looking backward is integral to the concept of hansei, the Japanese term for reflection. Done right, it more closely resembles introspection. One practical way of I conduct a form of hansei (for there as many different ways as there are people) is something I picked up from Seth Godin: reviewing your “shipping list” (aka stuff out the door) for the year in review. The late Steve Jobs always maintained that “real artists ship.”

I follow that with a more conventional after-action review, in which I seek out the gaps between what I expected to happen and what actually happened–for those are opportunities to learn, especially when the utterly unexpected happens, which for me it did.

But first things first. My 2012 shipping list goes something like this:

Of all those, I’m satisfied most with achieving the four big goals I had going into 2012: publishing my new book, writing for HBR, writing for Fast Company Design, and nailing a spot at SXSW 2013.

Now, as far as the unexpected. I did not in my wildest, darkest, most far-reaching corners of my brain expect to have two 20mm titanium stents put into the left descending artery of my heart (aka “the widow maker.”) That’s a Black Swan of the deadliest variety. I’m an active guy, cyclist and tennis player, I maintain a bodyfat percentage in the 8% range, and swig water like there’s no tomorrow. But that’s where the learning comes in.

What I learned from this little incident, and this is something applicable to both business and life, is that vanity metrics are deceiving and deadly. What is visible on the outside may have little bearing on your true health. “Six pack abs,” low bodyfat, etc are great brag points, but they do not indicate true health. So, beware of what you’re measuring…it may just lead you astray.

I also learned that I have what Nassim Nicholas Taleb refers to as “antifragile” characteristics in his amazing book by the same name. In other words, I got stronger from that Black Swan (also the title of his previous book) event, not weaker or more fragile.

As you look forward to the New Year, don’t ignore 2012. Invoke the spirit of Janus. As Sakichi Toyoda maintained: “May your future be lit with the knowledge of the past.”