Yes, of course there are a lot of examples of people who had gotten into bitcoin, and they ended up selling too much bitcoin too soon, and then they end up experiencing psychological difficulties to get back into bitcoin by buying more bitcoin at a higher price than the price they had sold.  We have a lot of those kinds of examples, and even some of those folks were very profitable in terms of dollars of how much they had sold, but then they are not so much in profits if they figure out if they had held onto more of their bitcoin rather than selling them all.

I think that people can still learn from their past mistakes to get back into bitcoin, and even if they do not get back in BIG, then at least just get back into bitcoin in a way that is relatively comfortable for them, whether that is making a lump sum investment, buying on dips or a DCA strategy.  I personally recommend a DCA strategy, but of course, if someone is more experienced with bitcoin, they might feel better to buy in a lump sum or to employ various buying on dip techniques.

For me, the DCA method seems better, even for folks who had sold too much BTC too soon in earlier times, because they may well have not felt as comfortable with holding bitcoin, but if they DCA over a longer period of time, then they might be able to build more confidence with BTC as an investment and then even start to feel more confidence to even supplement their DCA strategy with buying on dips and also lump sum investing.

Another thing that many investors into BTC have to try to stay aware is that there are risks holding BTC with third parties, and in the beginning of their investment into BTC their BTC might not be worth very much, so it may well not matter if they hold most if not all of their BTC with third parties (such as on exchanges), but as their BTC increases in value, they may well need to study into ways to hold their BTC in other ways, such as on a private wallet, and there can be some needs to spend some time learning about the various private wallet options, and some of them are more comfortable than others, but there are still risks (and learning curves) in terms of holding your own BTC (holding your private keys rather than leaving them with exchanges, in which you really do not own them if they are held by third parties rather than holding them yourself, but if you hold them yourself, no one is going to save you if you fuck up your security or you lock yourself out of your own coins in one way or another.  So it is not necessarily easy being your own bank, even though it may be more empowering, but some people might not even be sufficiently competent to be able to do it without some assistance from others... and even smart people might end up losing their coins.