“Invest only what you’re willing to lose” is terrible advice because it
a) Frames investing as gambling
b) Ignores the fact that fiat cash is a position, and a terrible one over any extended timeframe
Discussion
BUT- if you’re unwilling to lose it, won’t you capitulate at a local bottom?
I think that’s where position sizing and volatility of the asset come into play (e.g., you probably need more conviction and willingness to experience a large drawdown if putting X% of net worth in ETH vs X% of net worth in SPX).