smarterAvgBear
It's kinda odd that the best terminal app is on OSX but not in linux :(. iterm is one reason I am postponing switching to linux from osx for my work laptop.
* It's basically a collection of text files
* Uses a markdown like syntax
* Has built in git support, so you can use git for versioning and looking at edit history.
* There is a gui that let's you edit in wysiwyg style * Can link between pages
* Written in python, so pretty much runs anywhere (no proper android/ios app still though)
* Todo item support
* most importantly, it's open source
* plugin system so you can add functionality easily
I pretty much use this as a knowledge management, daily task tracking system. It has a journal plugin that essentially creates a files for each day, similar to what you are doing.
I have it for both work and personal stuff.