Elizabeth,
I find the use of navigating interesting, especially as it has even quite physically been done 'by the stars'. However, with the question put to you here I felt the internal and external aspects were not just a navigation system.
Partly why others are so limited in 'predicting' our futures for us is because human beings have choice at every stage. This means that for every new piece of information we receive we can adjust the next outcome.
Sometimes we take the 'messages' we receive as being confirmation of previous decisions only to find at the next point it isn't that straight forward. Other times we take them as guidance to look in a particular direction, and find a possibility extra to what we were already intuiting.
Whatever the outer manifestation we each have our interpretation and sense of alignment with it to whatever percent at that time. It is a continual feedback loop - just like so many physical systems within our bodies - that means we are making our own roads as we reach them and consider the conditions they allow us to drive in. Sometimes we forge ahead regardless and break through barriers that at other times will not let us through at all. Sometimes we turn away only to be lead back to the same point from a different angle.
Conditions are determined by our own perceptions of them, and how we trust our own readings. As they say, the map is not the territory, but the closer the map - our intentions, hopes, previous experiences and expectations for other possibilities - aligns with the circumstances of the world we find ourselves in, the more likely we are to tell ourselves that this is just where we are meant to be.
Most interesting of all is to decide when a map just has nothing to do with the journey you want to be on. Columbus did not step off the edge of someone else's flat world - he knew of other possibilities many others were already talking about. Then he made his own map to share his experience with others.
That is what many writers are doing - sharing worlds that invite others to go exploring in, and beyond!