You can trust both!
You dont need to choose since both things can really be possibly for you to engage on without needing to focus because you do really need both specially fiat.
Even if we do hate up centralization but still we are heavily dependent in fiat and other centralized institutions and we cant really deny such thing.
Dont focus on one because even how hard you do believe on crypto, fiat would still remain no matter what.
Fiat is a necessary evil because of the fact that Bitcoin's adoption rate hasn't reached the level that fiat has attained. But I'm definitely sure that when bitcoin is accepted at most online and offline merchant stores then fiat relevance would drop significantly and even start to become less used. If there one thing fiat is good at, it's the adoption level and until bitcoin reaches such level, we would still have to make do with fiat and traditional banking systems even though its proven that they shouldn't be used further or trusted. Like I said, it's a necessary evil. We don't like it but there's no choice.
For that to happen Bitcoin would need quite an extremely level of price stability. The stores accepting Bitcoin these days still go through a fiat conversion channel immediately, which the translates into fiat not losing quite the relevance.The only way is stable cryptos, but they must be pegged to something as well. What banks can't do is rob you off with hidden fees or (even illegal) interest rates on credit cards and so on.