There's a reason to-do lists help you get things done. Pick up milk? Check. Drop off laundry? Feed dogs? Vacuum? Check, check, check. Integrating this checks-and-balances system into less categorical areas of your life- do more good? have more fun? take more risks?- is a little trickier.
The Happiness Project author Gretchen Rubin untangles the thought process of how to measure those things that matter but are hard to keep track of.