Take a step back, then move forward one step at a time. When facing the stress of a deadline, it's easy to become overwhelmed by everything you must accomplish. Then deal with your tasks in small, logical, progressive bits. Before you know it, you will have met your deadline. Learn from your mistakes.
Nobody is perfect.
Rather than dwelling on what you did wrong, figure out what you can learn from the situation. Be sure to take note of what you did well, too. When it gets to be too much, take a break. Or spend five minutes doing dishes. The trick is to walk away from your work and clear your head.