Sure, I get what you are saying, and yes, my portfolio is still quite out of balance. I am taking on a lot more risk than I need or want, so the cure is to move more AAPL, for that reason alone.
If you've been in AAPL for as long as I have, you'll remember the big hits it's taken over the last 20 years. The first was in 2000 (or was it 2001?) when it dropped 30% in one after-hours session, and then went lower. Would that have been a good time to sell? Then again in 2009. And again in 2015. Would any of those been good selling opportunities? Basic human instinct is to follow the herd and anybody who thinks they are a true contrarian who can read peaks and valleys is probably kidding themselves.
I don't give myself that kind of credit, if only because I know that even the people who spend their entire lives trying to read and time the markets are pretty poor at it. More often, you are going to do just the opposite of what you should be doing because your emotions (fear and greed) are feeding your decision-making more than you will ever know.
The tactic that has worked for me in managing my investments is a certain amount of deliberate ignorance. I do not look at my portfolio daily, or even weekly. Sometimes, not even monthly. I avoid staring into the hairy eyeball of the market to try to figure out what it is telling me. I am aware its hypnotic affect will cause me to do stupid things. I am not superhuman and I know it.
The ETF program I've been into for the last several years is basically set-and-forget. You select a risk level (equities vs. bonds), push the button and walk away. They buy you into a dozen or so low-cost passively managed ETFs that cover the entire market and keep them balanced. It is a blissfully dull method of investing. I can highly recommend it, especially if you've had your stomach in your mouth a few too many times over the years.