I agree that keeping a record of completed tasks can be really useful and important. I use software named DayNotez to keep a journal of completed tasks. I can quickly search for an entry to see if I did something or not. Or when I did it. It's great to be able to call someone and say, "I mailed the request form on September 23 but still haven't gotten it." People take you seriously when you know the details like that. It's also great for resolving arguments with my spouse: "No, we did X 2 days ago, not 2 weeks ago." I'm really not kidding.

-andersons