The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( TheStreet) -- The euro was born in January 1999, which means the European common currency will turn 13 in January. When I was 13, I never wanted my hair cut as short as my mother did. So we would negotiate -- sometimes right down to the final snip in the barber chair. Neither of us was happy, but we could both live with the outcome. This appears to be the key issue for the stock market as it reacts to the amount of the "haircut" in the ongoing Greek debt negotiations. The S&P 500 Index gained for a third consecutive week, marking the first time that has happened since February. Last week once again featured solid and better-than-expected economic data and earnings reports and no breakthroughs on European debt problems -- although discussions seemed to progress on the amount of the Greek bond "haircut." The S&P 500 Index closed the week at 1238, basically flat for the year, and up 13% from the low of Oct. 3.