The hardest part of any project, for me at least, is starting. That first step, first word, first action, is always the hardest. Once I've done that I can start gathering momentum and keep rolling. The thing itself provides part of the motivation to continue as there is part of it already. But that initial plan can so easily be thwarted by inaction. It is far too easy not to do anything, that some days nothing gets done.
For me, the rubber his the road as soon as I tell someone I'm going to have something ready by a certain time.