It's your life ticking by.

What is the next action
you could be doing
right now?

Is your next action stalled?

Is it a physical, visible action?
Word it as a physical activity yielding an artefact that can trigger the next action.
Is it a single, atomic activity?
Acknowledge the multiple steps: move this thing to "Projects" and identify the next physical, visible action.
Could it be better worded?
Write your next actions as declarative statements of the actions that will be taken to achieve the goal.
Is it the very next action?
Walk backwards from your goal to derive the next physical action.
Have you defined "done"?
Begin with the end in mind - have a goal. Have a clear idea of what your world will look like when this goal is accomplished.
Is it something you can't act on right now?
If taking action on the item involves calling someone: call them, or move it to @Person or @Phone context.
If you're waiting for someone to get back to you, tickle them, then move the action to @Person or "Waiting On", with a follow-up in your calendar or tickler file.
Are you actually committed to it?
Review your personal goals and mission statement to remind yourself why you chose to do this.
If you still can't find the motivation to do it, move it to "Someday/Maybe" or delegate it to someone who will own it. Delegate, dammit! (remember to move to @Waiting, calendar or tickler file to trigger follow-up)
Perhaps you're procrastinating
Choose something fun to do that will move you closer to your goals!
An homage to the work of Merlin Mann