Invest with the amount of money that you can afford to lose only means that what you want to invest on is highly volatile. That helps you to know how risky is what you want to invest in is.

If you invest big and you make huge amount of money, that is your luck. Or you invest hugely in it and you lose, that is it.

You should know how risky what you want to invest in is, research about the asset to know if that statement is entirely true or not, some investment are not that risky.

Like bitcoin, when the price decreased so significantly, you know you have more precentage in success rate, unlike when the price is high.

About altcoins, you know how gambling they are.