It's only a mistake if you're a speculator, trading Bitcoin as you would any other commodity, with the timeframe of days and weeks in mind instead of months and years. Price is secondary for me, I would take Bitcoin as payment over any other currency right now, crypto and fiat both, simply because I believe in its value and believe it can only appreciate for the long term. Sure, I need to sell a bit every now and then, but I sell what I need as soon as I have it, so again, price doesn't really matter to me for this requirement.
Those who bought at 20k may have to wait for months, the coins I got at 19k will also have to wait for months, possibly years. But that's perfectly all right.