Sagittarians are the hunters.
Thus, a challenge and a need to feel free are the two most important traits for a lively Sagittarian. Put them in a situation where he or she has work that is repetitive or makes no demands on them and they will crumble.
Their sense of fun is infectious and their positive, extroverted enthusiasm is second to none.
They make exhilarating partners in spite of their need for freedom.