Just as two people together are often more than twice as creative and effective as either working alone, solving two problems at once is generally more than twice as difficult as solving one. The network effects work in both directions. When you have two major issues, information about them both is fighting for your attention and brainpower, and the fight itself uses up extra energy that neither problem would on its own.
The first thing to do: isolate. As hard as it might seem, you have to pick one thing and tackle it. Call in backup if you need to – not to solve the other problem, but just to keep you on task. Write down the other thing and put it aside, telling your brain that it’s coming soon but not to otherwise worry about it.
Use whatever tricks you have to censor out incoming information about that problem. Disable updates, turn off your phone, or leave that room. Tackle the one thing first, get it stable if you can’t solve it completely. When you get to that point, you can switch to 100% focus on the other.
Part of your brain will scream that the other thing needs your attention, but that’s exactly the thing that’s making both problems harder. The total time to solve both issues will be lower if you do one thing at a time.
The Opportunity Machine 