I was going to write an insightful response here, but lunch time came up and well, I'll get to it later. :)

Seriously, though, I've found that procrastination is my greatest hurdle to overcome. I always think: "I'll get to it later", or "There will always be time to get to that". Invariably, all that time ends up getting away from me and I feel down on myself for not getting to said project/essay/whatever.

So, when you have an idea, act on it. Don't wait, because waiting will kill that nascent idea as surely as anything. Make time, even if it's just a few minutes, it will end up benefiting your project in the long run.