Reducing friction is what worked for me. I've been using a headache tracking app for a few months now. I had to sort through a bunch of bad apps. Eventually I settled on one that only requires three taps to log symptoms after it sends a notification once a day (the key is you can set custom buttons to record the specific info you want). That's low enough overhead that I stick with it, and because of that I actually discovered and was able to address the root cause of my headaches, which is life-changing for me!

For something even lower friction than that, I just got this new device "Index 01" https://repebble.com/index. It's a ring with one button that you can hold down and dictate short voice notes to yourself that are transcribed and saved on your phone, set reminders and alarms, etc. It's super low friction because it's always there, you can do it one-handed, and you don't need to get out your phone so there's no distraction. The software is open source and hackable too, so you can customize what it does with the notes and add new voice commands. I think it would be perfect for low friction journaling of illness symptoms.

There's also a Pebble app called "Notes to Self": push button, dictate note, note gets transcribed and added to the timeline, either in the past (if note lacks a timestamp or is in the past) or for a future reminder. It's been the lowest friction for me to set reminders or save notes to myself about things that happened.

https://apps.repebble.com/notes-to-self_1bf71e21cd18409baa8e...