The idea of investing no more than you can afford to lose is the same as making sure that you are investing within your discretionary income and not using money that you need for expenses. Also bitcoin is not guaranteed to be successful, so everyone should realize that he could lose up to 100% of what he puts into bitcoin. Surely no one invests into bitcoin (or anything else) or even engages in trading with any intention to lose, yet they still need to account for the possibility that they are not using money that they need for their expenses whether expenses in the coming month or two or even expenses down the road.
That’s true eventually as, the idea of how Bitcoin investments should be approached and I agree on the not having a 100% guarantee on it but, it has some guarantee none the less, especially when compared with the many altcoins out there. Bitcoin has more proven guarantee then the lots of them, deeply rooted in its price history and how it’s carried despite many critic and attacks.
They need to settle up their expectation towards their investment since everything has a risk that's why its always good to think about in more realistic way that bitcoin is not a quick rich scheme where they can always get rich in future. There's always consequences so if people doesn't want to lose their money since that amount they put is the one they can't afford to lose then as stated don't invest with bitcoin since somehow it doesn't offer any sure profit to the investor. What we only have here is the historical data that all holders is gaining and the technology and adaption of bitcoin is growing. So if we are lucky to get huge earnings in future then this is really great for us but if not since there's something bad happen with bitcoin then it still fine that is part of the challenge in life that's why use only the amount you can afford to lose since this thinking could provably help us to condition our mind towards many possibilities that might happen.