A person who thinks all the time has nothing to think about except thoughts, so he loses touch with reality and lives in a world of illusions.
— Alan Watts
An interesting quote to keep in mind while designing Shimatta. Shimatta's goal is to capture thoughts based on your daily experiences and learnings. It shouldn't actively force you to think about stuff that you could write down just for the sake of doing so. But what if a thought occurs but you're not in the habit of writing them down or you forget doing so?
A solution for this could be to let the user setup individual reminders. Reminders that will be sent at a moment the user thinks is the best time to reflect on his thoughts. Be it in the evening or the next morning those thoughts occurred.
Also just reminding a user "what was on your mind today?" might be to generic. Everyone is different, everyone does different things during the day. I for example stumble across interesting articles or programming libraries during the day which I might want to keep in mind. So my reminder should ask me:
"Have you found any interesting links today? What's interesting about them and how will you be able to implement them in the future?"
Of course, those are just thoughts about improving how to write down thoughts. And as the initial quote said, just thinking without doing detaches you from reality. I don't know if the described solution above is useful unless I built it and tried it out.