For every creative endeavor - be it writing, or coding, or whatever - starting off is often the hardest part.
You have an idea, you know it is good, but you can't bring yourself to turn it into a reality. You put off, you dally, you find a hundred urgent things that simply must be completed before you can get started.
But then, kicking and screaming, pushing and shoving, you get yourself started, and it starts to flow. You work up some speed, start digging into it, and the more you dig the more you become aware of two things: first, that you are on to something good, and second, that it will take an enormous amount of energy to get it done the way you visioned it.
But there comes a point when you become so engrossed that your project becomes your life and it starts pulling you in. Far from fighting to get started, you have to fight to pull yourself away from it.
This critical point, this passover from pushing to get something done to getting pulled into it completely is, for want of a better term the "Aha" moment.