Intense Pressure Yields Mistakes?

Today I had what I felt was some intense pressure to accomplish a goal.  I wasn't sure where to turn.  The pressure resulted from a time limit on my activities to produce.  The task was simple.  Yet, I couldn't do it.  I couldn't think clearly at all.  Instead, I jumped from one place to another (one data set to another) and dug myself little meaningless holes for about an hour, until I was yelled at by my boss.  Then, for whatever reason, I completed the task within ten minutes.  The issue was that the data set I was first using was dug up (pulled from a larger data set) by someone else, and wasn't current.  I had to sort of back into some numbers to figure out what was correct, but I did it.  And I did it really fast.  And efficiently, if you don't count the first hour of frenetic bullshit.  My question is: how to freeze out the first hour and just act.