Spiritual Meaning:
One-pointedness and bigotry are not qualities that are particularly spiritual, but self-discipline may require us to keep to the ‘straight and narrow’.

Psychological / Emotional Perspective:
A narrow bridge might suggest a difficulty in communication, perhaps in putting our ideas across. We should take care not to be narrow-minded and judgemental in our dealings with other people. We may be intolerant and parochial in our opinions.

Everyday Material Aspects:
When we dream of anything that is narrow, we are aware of restrictions and limitations. Sometimes we have created them ourselves, sometimes other people will have created them for us. A narrow road would perhaps suggest some kind of restriction, and a warning that we must not deviate from our path. A narrowboat highlights the meaning of a boat with the tendency to put additional restrictions in place.

You might like to consult the entry for Boat / Ship.