I don't remember where I got it from exactly, but what really brought this home for me was the bookmark metaphor one of the coaches brought up in a webinar (I think).

The next actions on your context lists are like a bookmark. But you don't just read one page, put the bookmark in, and then switch to the next bookmark in a different book. Instead, we continue to read and when it is called for, we put the bookmark back in where we left of (ie. put down the next action that has to follow after we stop working on a project).