No Stupid Questions

This is actually a problem in scientific note taking and the very simple rule is you write all notes in pen and if you are needing to remove text you only use a single line to cross it out. That way if someone scribbles out the words/data you know it was tampered with as opposed to modified by the original writer. It also helps to put your initials on every edit and sign the end of the page, as well as have a witness sign the end of the page (but that may be excessive in your case). Also use only bound notebooks with numbered pages that are obvious if a page has been removed.

Maybe there's a technical solution but what if you forget to check it?

Anyway watch the movie "Memento" if you haven't.

Write your journal by hand, with a pen or pencil on paper. You'll know you wrote it because it's your handwriting.

It all depends on your threat model, what is your fear? I personally would be very comfortable noting stuff down on a notebook, or even having a random text file on my PC, neither of those is likely to get compromised/tampered. Let's assume you have someone living with you that you can't trust, and you don't want them to either be able to alter or read your entries, notebook and text files are not enough, but you can encrypt the notebook using any multitude of ways (including inventing your own language and symbols) and you can password encrypt the file in your PC. They could still destroy entries or the entire thing, if that is more of your concern then having backups might be more important. If you're worried about altering past entries you can use something similar to a Blockchain, where the hash of your previous message is used in the new one so it's obvious if someone erased a message, in the notebook you can do something like starting each message with the 5th to last word from the previous one or in some other way reference it.

At the end of the day it all depends on what is it you're afraid could happen to your entries, so we'll need more information on that.

If you have memory problems, how would you remember the system?

You could invent your own. It wouldn’t stop someone who was really determined to trick you, because the tradeoff between convenience and perfect security would likely leave you vulnerable to reverse engineering. But that being said, you can take your message, reverse it, Caesar cypher it, replace letters with numbers, drop vowels or spaces, etc etc until you’ve mangled it into a “hash” that only you know how to produce.

I write things down by hand and it doesn't matter if they are tampered with because it's just the act of writing the thing down that makes it stick in my memory; I never actually need the note after.

A seal of some kind. that's what they were used for in the past.

Pull an eyelash or similar, keep it between a specific page and check every time that it's still there. If someone tampers with the journal it will fall out and they won't realize it matters.

Set up a code to yourself, easily remembered, and don't share it with anyone. Then include it secretly in communications to yourself. If you don't remember sending it, but it has your code, you can trust it.

I really need to quit smoking weed

Learn one of the old shorthands

Not the best idea, but use a write once read many S3 bucket. That way once the note is stored it's not going anywhere or getting edited, AWS can do that and also backblaze.

Joplin - free encrypted and password protected notetaking app.

There's also standard notes, though i haven't used that one. Free and paid versions

If you really want to know something hasn't been tampered with though, look into git. You can use it raw or with something like VS Studio . Git can let you pgp sign stuff so you can know with certainty you made the change... unless you pgp key was compromised. Your changes ("commits") would be signed and time stamped. You can keep files locally or send to a git forge (github, gitlab, forgejo).

Git tutorial

Best of luck

if you are able to remember the method to create the signatures then you can do many things e.g a simplified digital signature. but if you can't remember a method then you can't ensure that someone else has forged a signature, because if you forget everything then you have the same information as anyone else and anything you can do, they can also do

apology for word salad

system which you can verify that its not tampered with?

Blockchain technology is one possibility to store data in a way that it cannot be changed later.

Does an immutable password protected journal suffice? Or do you need the ability to edit past entries? Or do others need the ability to read entries without the password?

Sounds like a use for the environmentally destructive technology known as blockchain.