How do you measure your productivity?
Other times, I'm pretty happy with my productivity after a day of work but when I really think hard about it, I see that I didn't accomplish so much.
And also, sometimes I don't know whether I'm going slow because I don't have much experience with the particular kind of problem I'm working on, or am I taking a wrong approach, or do I lack some critical knowledge that would make the job much easier?...
How do you measure your productivity?