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.
Interest on bank savings will generally barely beat inflation if they beat it, it's the worst investment possible especially in this area of low interest rates and sunset of the Dollar which will lose most its purchasing power in the coming decade
If the FED keeps interest rates low and create a lot of USD it is very bad for fiat holders and this is exactly what the FED has been doing and will do even more when they think they need to to buy some more time
Interest on savings accounts almost never beat inflation. Interest on savings accounts is so pitifully low it's not even funny.