2; Investment has zero risk but demands your patient to get you rich or successful probably in a long term.
Everything has risk, and difference is only more or less risk.
If investment is zero-risk, there would be no saying like "I
nvest what you can afford to lose".
If you understand the saying, you know there is risk of investment including Bitcoin investment.
I can equally say the phrase is wrong because your possibilities to loose lies on you because should understand the market is volatile before you can invest. There is absolutely no gambling there to find necessity of that term "Invest with what you can afford to loose".
So there is nothing to fear about in investing in bitcoin rather you only have to checkmate on your emotions and your bankrolls with how sustainable or unsustainable it can carry you in a period of time. So when you panic or sell at lost it is up to you and not the market.
So I take that term to be applicable in gambling or any of those prediction market like trading which once you looses you can't retrieve back your money unlike investment that at Dip or Bear when it affects your holding, definitely it will rise again on the bullish.
Instead, let the term be rephrased to "
invest with what you can afford to let go in the long term"