Some investors got to bitcoin early, yet did not recognize what they had, so they end up selling way too much too soon, so instead of continuing to buy bitcoin and making sure that they are continuing to build their wealth, they see 2x, 5x, 10x or even higher levels of profits in dollars, so then they end up selling way too much too soon, and based on their own income, they are not able to accumulate nearly as many bitcoin as they previously had with anywhere close to the same amount that they had invested earlier.. .so yeah, maybe they will come around to buying bitcoin again, but it can become psychologically difficult to switch from an accumulator to a trader and then to get back into accumulating, becuase there may welll be a realization that BTC buys may well end up being made for way higher prices than the earlier sales.. so that causes psychological difficulties.
Actually you can't blame those early Bitcoin investors who sold their Bitcoin way too early because just like some people are gambling on altcoins now that was basically how the early investors where doing same with Bitcoin because it was just a coin that was new into the market so no one would have given their 100% trust as at then and it's almost impossible to trust any system that just got introduced and has not gotten much attention and recognition by a large number of people so that was what happened among those early Bitcoin investors but now that they have seen the growth of Bitcoin I believe they won't find it difficult to buy at a high price now when they try to consider the price they bought it years back so the most important thing is having the finance to start now because with the height we all are anticipating the price of Bitcoin to reach, it's still at an affordable price now and buying Bitcoin doesn't mean we should go an all in or buy 1 BTC at a go, they can basically start accumulating now and hodl a reasonable amount that will boost their portfolio in time coming.
I totally agree with you and I believe if most of us that are currently buying Bitcoin at the moment were in their shoes, we would have also sold part of our holding at the point when we're in 5x to 10x profit. It's nothing to make a big deal out of it but it's now an issue when we've seen the effect of thier action and we're still gambling with our holdings and still selling at any slight profit we've seen or waiting for Bitcoin to get to $100k so we will sell and instead of talking about how to accumulate more Bitcoin which will place us in a good profit, it's now about trading our little Bitcoin or diversification which goes on to shrink our asset.
I understand the psychological difficulties you are talking about but they don't need to continue dwelling in the past as Bitcoin has even proven to be more trustworthy now than when it was earlier invented. So the only thing now is to accept the mistakes of the past and move on to start making accumulations.
Sometimes it's best not to take certain actions than after taking the action you now struggle to cope with the effects of your action. Almost all the people who sold Bitcoin way too early and now see Bitcoin at the current price are in a state of regret and psychologically, just like @JayJuanGee earlier said, it's going to be a tough one for them to come back and start buying at a price that's far above what they sold their Bitcoin at. It's even better that they probably sold because they felt they were in profit and not necessarily because they wanted to buy back at a cheaper rate which is what most traders do nowadays.
I believe we who are now the current set of investors are at a better advantage than earlier investors and we can actually learn from the mistakes they've made and ensure that we don't repeat those mistakes.