Your metrics are there to help guide future decisions to help you business grow better and stronger. 

Focusing on one metric alone can lead to skewed results and present false conclusions. If you are basing your key business decisions on that one metric, that's like balancing on a tight rope with no safety net, hoping you have assessed your next move properly and wishing for the best.

Part of the problem is not having ironed out the strategy first. Without the strategy what are you measuring? How do you even know what to measure?

For example if you are focusing your content on lead generation your key metrics could be return visitor rate or lead conversions. 

Try using a triangulated approach and your foundation will be solid.