Bitcoin is built up on trust. You need to trust everything in the Bitcoin world what is not decentralized! So actually you can only trust the network, because it will (actually) never fail.
You seem to contradict yourself, but I think you made your point.
I trade in moderate size transactions but never leave them on exchanges for more than a couple of hours. Then if I want to trade BTC for fiat I use Coinbase to wire it straight into my bank account.