Only invest what you can afford to lose is most generally use for newbies whom you are just bringing to the market and for people on social media when giving a general advise but the OGs now understand this market that bitcoin is bigger than what it seems now regardless of price correction. I have coins I have locked up in my hardware wallet, let it be there from now till 5years.
Not just newbies, this could apply even to people like Warren Buffett, it's just a matter of scale that we never think that they're going to lose any money. It's still a pretty solid advice in my opinion, it's not like it doesn't lead people to harm's way.