The answer is not to let the pressure get to you, and how you do this will depend to large extent on where the pressure is coming from. One quite common form of pressure is having tasks coming your way far too close together - you have hardly got to grips with a problem before another one lands in your in-tray. If you just stop Task A and start on Task B, then Task C and so on, you will never finish anything and the pressure will only get worse. The solution is to finish one task before starting another - except when the second task makes the first one unnecessary.