To make purchases with bitcoin is only worthless if you don't replenish your portfolio from times to times, through DCA, for an example. But if you are constantly acquiring new portions of BTC, it won't be an issue to pay for goods and services with bitcoin, as it just mean you are swaping fiat into crypto to use it as money on the present moment, without prejudicing your long term profit potential.
The pizza guy who spent 30 bitcoins was mentioned, but even him shouldn't feel bad about it, because if he had 30 BTCs for a pizza, I believe he had much more for holding purposes... It wasn't spending 30 BTCs in a pizza that prevented this guy from getting millionaire through BTC and it won't be your daily purchases with BTC that will prevent you from profiting from the investment futurely.
The guy who paid 30 BTC for pizza never thought the cryptocurrency would become as valuable as it is right now. He just considered Bitcoin as a currency. Not a long-term investment or a store of value. The original purpose of Bitcoin is to be used as "Peer to Peer Electronic Cash", so I don't get why people are so focused on its market price. 1 BTC = 1 BTC, right? Unfortunately, the world is reluctant to switch towards the "Bitcoin Standard", so most people will either spend or "hodl" BTC depending on current market conditions.
If you're really worried about losing purchasing power in the short term because of the volatility, then use stablecoins instead. BTC is growing in popularity each day, so it should only be a matter of time before a wide number of merchants worldwide accept it as payment method. Just my opinion