I had grave second thoughts and questioned my own reasoning. However, I had looked at the money and how much it really would help my parents. It was a lot of money for them. That's how every investor should look at their stock gains. If it's a lot of money, take it.
Some investors hold onto their gains solely to avoid paying the taxes when they sell.
Tax strategies should never discourage selling when you have a big gain in a top-heavy market. Years ago I invested substantial profits in new ventures to avoid taxes. I came to rue the day. I would have been much better off paying the taxes. It's pure speculation on my part, but having watched carefully the market corrections of the past few years, it seemed that each time a downturn threatened to get out of hand, a powerful surge of buying would appear.