Productive v unproductive worries
Productive worries are those concerning situations which we have control over. Time spent thinking about these situations may result in our taking action and therefore being productive.
Unproductive worries, conversely, concern things out with our control. Time spent on these is ultimately wasted and will make no difference to their outcome. Sadly, the only thing we will have to show for the time spent on these situations will be the undue stress all the worrying caused.