Neither the thought before nor the thought after a dash has to be a complete sentence. Sometimes a dash is used to emphasize a short, initial thought:
Keeping your wits about you‚‚that's the first rule of survival in an emergency.
A dash can also serve to link particulars to a summary statement:
Fast-moving, assertive, competitive, outspoken, blunt‚‚these are the characteristics of a director-type personality.
In addition, dashes can link complete sentences:
Such individuals try to shape their environments and relationships‚‚often they are unsuccessful.