Therefore, I have looked for a system for which data entry is relatively easy. I currently track my mood through a local  TiddlyWiki  combined with Noteself .
I have been doing it for a 6 weeks now and it seems to work fine and have learned a thing or two about myself that I otherwise wouldn't have.
 I store it locally and back it up.
Its open source too, I think.
Saving on Dropbox etc (can be done from client) might be a middle road if one trusts them more.
keep it up!
Another features I am considering applying are voice recordings and sharing with close friends. Do you have an opinion about these features?
It is on the web (rather than an app), so you don't have to worry with backups, changing phones, etc. And if you like to write, it is better to write on a desktop.
If you are interested, please let me know what you think.
I understand then it's harder to monetize, but you don't need infrastructure if it runs locally and for the user it's a privacy (security) win. Consider that people are gonna use it as a diary/journal and IMO having this saved in the cloud is extremely privacy intrusive so I'd at least would expect more info about encryption of data at rest. There is no end to end encryption so I assume this is by design and people will see ads in future based on their "mood"?
I think it's not ethical to extract money from users this way in 2019. There is no value-add from it being in the cloud (you wouldn't have any problem with scaling infra cost if it runs locally).
Also security headers: https://securityheaders.com/?q=https%3A%2F%2Fwww.quidsentio....
fwiw I find the idea itself quite cool but in it's current design wouldn't touch it with a stick.
I am thinking about the best way to secure the information, I am just not sure about the tradeoffs.
edit: thanks for the security headers link, I will work on it