I did that not too long ago (end of 2020). Probably mentioned it a couple of times since.
This was almost a full year before the eventual ATH -- I couldn't have known it at the time, but Bitcoin approaching 2017 ATH was already a huge signal of intent and for me a sure marker for a rally.
But circumstances required the cash, and I really didn't have a choice. So I sold most of what I'd built up over the years, with a twinge of regret, but still pleased that overall, I'd come into cash I couldn't otherwise have had saving in fiat.
DCA continued since, so I'm probably even "underwater" at these prices, as we're barely at $25k but I'm confident I'd still have saved up enough to have more on my next liquidation, than if I chose to keep in fiat.
You still profit when you have been holding it for many years so I do not think you should regret it too much. No one knows how much Bitcoin will be and there is a risk to holding all your money in Bitcoin because it could fail. We have seen countries ban Bitcoin in the past and they still ban it from being used but other countries have decided to allow it but ban Bitcoin mining. I think we will see more laws in the future about Bitcoin and as long as it is not banned outright I am happy about it because it will allow more people to use Bitcoin instead of banks. Bitcoin will probably reach its price limit in the next decade and hopefully become stable for businesses to adopt it.