A paper-only journal would defend against the state, but not against people you live with. A digital journal can be encrypted, but an intelligence agency could potentially gain access (like, them reading your anti-government rants that may involve violence… that sort of stuff).
So… how to defend against both threats?
(Also, I just realized, paper journals cannot really be easily backed up…)
Veracrypt hidden volume attached to an air gapped system. Unless someone kicks down the door and grabs you faster than you can click once, no one is getting at, or will realize that data exists.
Could even put it on a USB drive, so killing it is as simple as yanking the USB. Hell, if the feds come sniffing, you could just toss that bitch in the microwave.