I just published LifeTracking (market://search?q=pname:com.lifetracking) and I invite you all to give it a shot. The application allows you to track any value (like your weight or number of pushups you do a day), as well as any time-consuming activities (like sleeping, working, watching TV, etc). You can also graph the data to see it visually, and analyze it.
The goal of the application is to help you know yourself and your schedule better. Hopefully, when you graph things side-by-side you'll see that your mood is directly linked to how many hours of sleep you got.
Let me know if you have any suggestions or questions.