There is a great venn diagram that Carl Richards (a.k.a. @BehaviorGap) has drawn that has a circle entitled 'Things that matter' and the other called 'Things you can control' 

Where these two circles overlap is where your focus should be, i.e. focus on what matters and what you can control. 

Ben Wilson from MPM Limited makes this point in this article. His business is growing despite what can sometimes feel like a doom and gloom environment created by our media. 

We may not be able to control the outcome of the Brexit negotiations but we can control how we lead our businesses and our staff through the uncertainty.