Create a new "Done" Tasks view (Like the "Due" Tasks view)
"Harvard Business School professor Teresa Amabile's research says keeping track of them will make you happier at work, more productive, and more motivated." (http://lifehacker.com/5958265).
It would be great to have a "Done" Tasks view so you could see at a glance the things you accomplished Today, Yesterday, Last Week, Earlier; kind of like the opposite of the "Due" Tasks view.
This new Done view would allow you at the end of the day to take a quick look at all the tasks you had completed during the day (or the previous day) aggregated across all of your task lists and feel a little bit of accomplishment for the work you were able to get done. It would also be handy as a type of joint historical view of all of the tasks that were completed at any given time historically.
You might have to put some sort of hard coded limit, dynamic filter, or initially collapsed groupings by year, since it might quickly get too large if you had to display everything ever completed on every list.)
Adminsashika (Admin, Checkvist) commented
Ryan, great idea and a very good technique. We'll think how to fit the "completed" view into our current UI. Thanks!