NEW YORK ( TheStreet) -- Relax, don't do it when you want to come unglued.If you own Apple ( AAPL), it's no sin to have sold somewhere along this recent plunge line, particularly if you were sitting on massive unrealized profits. Never a bad idea to take profits. At the same time, if you own AAPL, it ain't no sin to be glad you're alive. While doubling down, as a general strategy, can blow up a portfolio, it's a risk I would be willing to take with AAPL right now. I'm not sure I have ever seen a stock more "certain" (because nothing in life is ever certain, particularly on Wall Street) to make a more historic run in my lifetime. TheStreet contributor Jason Schwarz wrote an excellent article -- Apple Slingshot: Making Sense of the Apparently Irrational -- detailing the real reasons why the stock has tanked: Institutional selling as funds rebalance portfolios (bring AAPL allocations into more reasonable ranges) and the attendant year-end, capital gains tax-hike profit taking. Schwarz downplays the impact of recent noise -- everything from "MappleGate" to iPhone 5 supply constraint rumors to Steve Jobs's absence -- on the stock's steep fall. While I agree with Schwarz, this negativity certainly doesn't help. Plus, it could spook retail investors from taking advantage of the weakness. One size doesn't fit all, but, at these levels and at this point, the downside presents a life-size buying opportunity in AAPL. As the noise works itself out, I expect another parabolic run between now the end of January when Apple reports holiday quarter results. Here's why: A fiscal cliff deal. Apple will lead out that broad market rally. How soon we forget. Despite those supply constraints, Apple sold more iPhone 5 units in its first weekend of sales than it did iPhone 4S smartphones in the entire first month. comScore reported this in late September, yet investors largely ignored it in favor of the hysteria. As of this past weekend, you're looking at two to three weeks ship time on all iPhone 5 models. This spells pent-up demand in my world. Name another technology company selling smartphones and tablets to the consumer and enterprise facing this "problem." The verdict is in: I was right (link to recent CNBC appearance). iPad mini is kicking relative butt.