In my opinion some of the self-tracking tools border on obsessive-compulsive, but others can be quick and useful. Three tools that I have tried recently are Moodscope, 750 words, and I Done This. In all three applications you are prompted everyday by an email to respond. I find that using a daily email as a taskmaster motivates me and helps me to complete the activity promptly. I also like the fact that each tool includes some kind of analysis-- the number of words used, percentage of tasks completed, or average of quantified mood per day. The analysis includes plots, graphs, and statistics.
Conceivably the analytical tools help you to self-monitor and self-improve over time. Moodscope for example lets you share your daily results with a buddy. (I haven't tried this yet). This way your buddy can cheer you on, or sympathize with your plight. Studies show that mood improves with frequent monitoring. I Done This simply makes you feel accomplished because you've completed a task each day, even if a small one. Also, you anticipate the prompting, so you are more likely to plan to get something done each day!
In contrast I have found 750 words interesting but a bit challenging to complete each day.