You might like ActivityRecommender, which quantitatively measures and optimizes your happiness, motivation and efficiency:
1. Record what you've accomplished; reflect later
2. See what's correlated with future motivation
3. Check the graphs of time spent. Are you getting more motivated?
4. Run an efficiency experiment: agree to several tasks to do now. One is chosen randomly for you to do. In the future you'll do another one. The ratio of the time spent is an unbiased estimate of the ratio of your efficiency at these times. Compete against yourself!
5. Write down partial ideas to revisit later. Lazily sort them whenever you want, like a tournament. Turn them into ToDos when they're ready
6. See what's made you most happy/sad recently
7. Reminisce: see a randomly chosen, high-rated comment
8. Feedback! Whenever you do something, you see a positive/negative number, some (usually) encouraging words, and a button for more details
9. Receive suggestions for what's next: even request something Fun and at least as good as the game you're considering
(Disclosure: I'm the developer, of course)
Feedback is super appreciated!