When you're feel like you're under fire and about to leave the trenches, keeping these tips in mind can help you keep your head in the heat:
Don't over-schedule.
Know your priorities and organize your day, week or month around them. Face it, how many times were you ever able to fully cross-out all the things on your To-do list and have everything go precisely according to schedule? Jamming things into your day for the sake of a "full day" makes for unrealistic expectations and unnecessary hardship, and self-inflicted ones, at that. Build some lee-way in your day.
Leave room for things to happen on their own. This is very important. When you leave room for things to happen on their own, you don't force things into play once you've got the ball rolling. Hurrying things along only shows impatience and poor planning. If you have a plan and you're working things out from it, trust in yourself and your actions, and that you're doing what you can. Don't force it.
Focus. Know your major goals for the day, or the week, or the month, and don't get distracted by sudden surprises or daily tedium. These goals are part of the structure
with which you are building your life, you could waste valuable time and energy trying to make up for mistakes you make when you're not paying the right attention to the important things.
Know your most productive periods. People have their own internal rhythms, their peak hours. Know yours, and take advantage of these times by using them on your most important issues.
Clean up your mess. Rather than waste energy hunting for the things you need for work, keep a neat workspace. Deal with clutter ASAP. Even better, prepare for the next day at the end of your current workday. By laying things out in advance, you carry over un-addressed issues to a fresh day when you're better prepared, and by knowing what you'll need for the next day you save time.