> But to answer your question more directly, you should use a money that loses value because its purpose is as a medium of exchange and not a store of value

That's an odd definition of money. The ancient Greeks already thought that money is medium of exchange AND a store of value, and throughout history people have preferred money that held its value. It's also circular reasoning. A medium of exchange should lose value, so you should use money that loses value.

> you can instead "buy" a savings, or "buy" an index fund

So money that loses value creates inefficiencies in the economy, because people have to waste time worrying about preserving their wealth, investing, etc.

> You struggle with letting go with your currency

I still need to eat, to live somewhere, I want to experience things, a money that increases in value does not destroy my desire to consume.