Unless you're worth about $5M, you made a mistake in the past by anti-diversifying and stock picking. Had AAPL gone down, this mistake would be apparent. But instead it went up, which caused you to wonder if it wasn't a mistake.
Not all mistakes turn out badly. Oftentimes, they turn out great, like the time I fat-fingered an options order and went long instead of short, only to realize my error when I was up 100% instead of down 50%!
But in the long run stock picking involves taking on both market risk (beta) and company-specific risk when you could have just taken on market risk and done about as well. This tends to hold true in the long run, although short-term wins tend to convince us we are master stock-pickers.
Remember Samsung's exploding phones? Remember Blackberry's sudden slide into obsolesence after going a couple years without a technological breakthrough? Remember Windows phones? These are illustrations of company-specific risks, and they all occurred in companies at a time when their market was growing rapidly. These events seem obvious in hindsight, but few predicted all 3. For every portfolio loaded with AAPL in 2002, there was someone else loaded with Nokia, afraid of selling and missing further spectacular gains.
There are 5 ways to win Russian roulette, and only one way to lose. Congratulations on winning, but put down the revolver. Switch to Vanguard's Nasdaq ETF and be grateful it didn't require an eventual five-figure loss to learn not to stock pick. Behavioral economics says ignoring this advice is your destiny, because you won big in the past.
If you still need help seeing AAPL as just another company, read Clayton Christenson's "The Innovator's Dilemma" and consider that AAPL operates in the inherently vulnerable high end of the market. Also, the markets for cell phones, laptops, etc. have reached near saturation in the developed world. They're not technology any more than microwave ovens.