When I'm reading a book, I stop only at the end of a chapter and then pick up again from the next. 

I used to do the same with episodes of a series, but nowadays they are engineered to have a cliffhanger at the end of an episode which is resolved at the start of the next, so I stop when it is resolved rather than at the end of an episode.

When I'm working, I stop when I've concluded a task in its entirety. 

This provides me closure for what I was doing, and doesn't linger on my mind once I'm done with it. And I can then be totally present in whatever else I'm involved in later on.

However, if I do want it to linger, then I pause without closure. Like when I'm thinking about what to write or how to solve a problem. And then my mind continues to explore ideas even after I've actively stopped thinking about it. 

Our minds behave this way naturally. It is up to us to use it to our advantage.