Alphabet stock is down slightly from its November high. Here's why that's an opportunity, not a warning sign.Six years ago, on Dec. 23, 2019, I could have sold my Alphabet (GOOG +0.00%) (GOOGL 0.12%) shares at a market-crushing profit. After almost exactly nine years in my portfolio, my Alphabet Class A stock was up by 348%. The S&P 500 (^GSPC +0.32%) had gained 156% over the same period.But I didn't rebalance this successful position. Now, those Alphabet shares have gained a total of 2,084% (or 2,096% if y ...