Leap Year and Love

Today is a special day, it is TheWife's birthday and it has me thinking about love and couples.

Anecdotally and without evidence let me assert that we seem strangely good at finding mates that complement our lacks. People tend to couple off with folks who are not like them in important ways, ways that compensate for abilities or propensities that we wish we had. Yet, the initial impetus for the coupling is the "wow" moment in which we find ourselves attracted to someone seemingly without sufficient exposure to reasonably judge their capacity to fill in our missing pieces. We don't seem to miss enough to make it a hit or miss (or possibly a "hit on or miss") trial and error type procedure (although, yes many of us have made errors in this department). So why does it seem to work so well? How is it that we have the uncanny knack of finding someone who is very much in crucial ways our other half? Or is it as TheWife would tell it simply fate?