From Zen Habits comes a nice a summary of common hangups to productivity, and a list of quick reminders to help overcome.

Two of them stand out as common for me.

On starting:

Procrastination is one of the most common obstacles to Getting Stuff Done… so if we get good at starting, we’ll have conquered a huge obstacle. Starting is best done by focusing on the smallest first step, and practicing just launching into that. When I wanted to form the habit of running, I focused on just getting my shoes on and getting out the door. An art teacher I know tells students to just focus on getting the pencil to paper. Meditation teachers say to just get your butt on the cushion. Pick the tiniest first step, and launch into it.

And stepping back to see the big picture:

It’s one thing to be deeply focused on a task, but it’s another to step back and taking a look at the overall picture. I advocate doing that at the beginning and end of each day (a morning planning session and a brief evening review of your day) but also checking in during the day with how things are going and how you might need to adjust your plan and refocus yourself. We all get distracted, interrupted, waylaid by unforeseen difficulties. And those are all fine, if we can refocus ourselves as needed.