In terms of tags, my idea was to just allow people to drop any tag they want in (similar to tagging a post in wordpress) and have the system autocomplete their

In terms of tags, my idea was to just allow people to drop any tag they want in (similar to tagging a post in wordpress) and have the system autocomplete their tags when they're typing. That way, if someone is constantly tagging "mom" and their mood is low, after a while, you'll be able to positively associate the tag and the moods. In regards to your last bullet, yeah, compound insights are tricky. I still don't really have a solid system of doing these, but essentially you want some sort of rule-based system to pull it off. Please let me know if you find any resources on it, I'd love to help you with what you're working on.