There is a golden rule to live by: never invest what you cannot afford to lose.
FOLLOW IT.
This ^^ a million times over!
Let's say you are cannot afford to lose any of your savings so you don't invest anything then you have all your savings in fiat currency, investing in a currency that will lose its value over time
Your logic is flawed. The value of fiat savings actually generally will increase over time even though the principle will experience inflation as both investment returns and interest on bank savings generally will be greater then inflation.