I'm not sure I understand your comment (I don't know what you mean by "limit work-in-progress") but one of the principles is to be explicit and formal about all

I'm not sure I understand your comment (I don't know what you mean by "limit work-in-progress") but one of the principles is to be explicit and formal about all the projects you've got going, as opposed to having fuzzy ideas about an unlimited number of potential projects in your head. When you track all of these projects, you adopt a more realistic approach, and you think more carefully about whether or not to start one.