I don’t often just point to another article and not provide my own opinion on top of it, but Doug DeCarlo has the right approach for agile project managers in his article "Get It Right the Last Time: Developing an Agile Attitude".
If you are a project manager, agile is as much about mindset and attitude as it is specific process approach, techniques, tools or metrics. Learn to embrace the attitude, and allow the rest to evolve.