I clearly remember my first day on my first professional job.  Just out of college, I was sent to a training which included an hour or two about time management.  The trainer, a much older and wiser woman, told us all to repeat a little mantra after her.  The time management mantra was "Do it now!" 

I wish I had a five dollar bill for everytime I remembered- and applied- the mantra over the last 20 years. It has been one of my guiding lights to superior productivity.

David Allen, of Getting Things Done fame, (one of my personal favorite books) also has a version of "Do it now!"  He teaches his readers to "Do it now" but only if it will take you two minutes or less. 

If the task will take more than two minutes, Allen encourages his readers to capture the idea on their project list to get it out of their head.   

It works for me!  Try it and see if it works for you.