I shoved £500 down in Sept 2017 knowing full well it was a gamble, and still have a roughtly £500 balance now -- having skimmed enough off the top over the years to buy a couple of iPhones and whatever else. I 100% consider this profit to be literal dumb luck.

Unironic congratulations on being self-aware enough to take your profits without it affecting your reasoning. Anecdotally, not many seem to come out of crypto net positive with that mindset.