Today 1 BTC can get me a small house, tomorrow I don't know. That is volatility... even with the FIAT devaluation, I know how it devaluates, so I can plan ahead.
If fiat value is a concern you can hedge the risk to minimize any loss i.e
1. Purchase 1 BTC
2. Short CFD 1 BTC
or sell BTC Futures.
Never done these personally but principle of hedging is same whether with fiat or crypto.