I conducted an interview with David Allen, author of Getting Things Done, last week. One of the things we discussed is how people focus on what's out of control. The example he used was that if there's a hole in your ship, you're not worried about what course you're on, you focus on fixing the hole.
This makes sense for project planning. Have you been in the situation where you should be planning, but you're busy putting out a fire? You have to get the fire off your plate before you can get to planning. The key is to focus effectively so that you can get to the planning.
The technique provided in Getting Things Done is to identify what the next action is for any project or other task on your plate. When you can clearly identify the next actions, you are more effective in executing. Pick up the book if you want more details and look for an upcoming article in Projects at Work on the topic.