Since about January I've been moving between several methods of keeping track of everything I need to do. First I tried Google Tasks (through Gmail) but found it was difficult to remember to use it, though it was easy to add/edit task while away from my desk. Next I tried a more basic approach, use Tomboy Notes on Ubuntu, which stores and syncs your notes as well as supporting cross-references within notes. I held onto this for about a month, and I ended up with a decent body of information spread across many notes.
The solution I settled on recently has been much simpler than all that. I noticed in my notes (and previously tasks) that they were bunched into several categories (e.g. Work, Health, Hobbies, etc), and while I could group the notes into folders, but further than that I had my work notes in a separate lab notebook file, and all my fitness data in a physical notebook (that had been replaced a few times due to loss). I decided to use a single file and journal each day, with areas broken down as paragraphs. The only thing that makes this useful though is having specific information presented always with consistent formatting, making regular expressions an easy way to scrape data from it.
As each day starts with how much I slept, and ends with a few data regarding food intake and such, it's trivially easy to parse any given set of days into graphical format.
While the system isn't perfect, it does make it easier to review my days and orient myself on a local time line. This is especially valuable when work seems to make all the days blur together save for the weekend. I've noticed even just re-reading the entry for a single day before bed reminds me how long a day actually is.
I'll likely have to split each month into its own file to prevent compilation time from growing too long, but tweaking the code to parse multiple tex files is easy enough. I'll stick with this system until something else comes along, and post updates if it continues to prove useful. If anyone would like the scraping code, just ask in the comments; though writing it is good regex practice.