Breathe and stay centered in the now and in the body. Not the past, not the future.
Visualize in detail successful execution of the task at hand. Let the emotion set in.
Attack the task with all of who you are. Failure is not an option.
Just think about it. Every time you got really focused and in the zone your mind went through this process in one form or another. You took a moment to get centered, you thought about the outcome you wanted, and finally you went to work with fierce determination. Now think of the times you lost focus or didn’t zone in. One of the three steps were absent. Either you were distracted, you didn't have a clear goal, or you didn't approach the task with enough determination.
This is the day to day battle mantra, do this and your to do list will get knocked out in a cinch.