Which factor or factors do you consider to be your most significant challenge?

Decisions made at the administrative level may be influenced by many factors; these include suggestions or directives by elected officials, legal advisors, or court mandated change. You are in a position to influence change, to construct change, and to ultimately implement change. Which factor or factors do you consider to be your most significant challenge? What advice could you give on how to handle influential groups who may be at odds, such as a Mayor and a City Council?