If you're going to spend your time working, you might as well feel satisfied about getting things done. If you sometimes have the feeling that you've worked all day and got nothing done, that can sap your motivation.
Find out what the problem is and fix it. The main problem is that much of the work we do is somewhat intangible. But you can do something about it: Rather than, or in addition to, making a to-do list, you can make a done list. Learn more about it here: Motivation Principle Number Four.