When is enough enough?

When I start sewing, it is hard for me to know when I have done 'enough' for the day.  It's always so satisfying to get another seam done and another step completed, I want to just keep going.  Today I started on Barb's second Pioneer dress.  I did the collar/interfacing/facing, the yoke, and sewed the collar to the yoke and sewed on the yoke interfacing.  I think that has to be enough for today.