Indeed; also, I must be doing something wrong, because when I start breaking tasks down to the point of triviality, I end up with a rather big pile of them, which becomes its own challenge to manage - and then two or three simple tasks in, some result invalidates most of the rest of the breakdown.
The key is to figure out what is the priority, break that down to a couple tasks you can do now and do them even before you break down anymore. That is you want to find the list of what you will do in the next few hours and get that done. Done means find a good stopping point, clean up and put the tools away. Sometimes you will ready to clean up and realize you have more time and so you break down one more task, that is fine so long as you leave things in a finished state - cleaned up and tools put away.
Ideally the project is complete and whatever isn't done will be a next phase you can do in the future. If a project must be over several days you need more planning and you need to get the whole thing done. For your daily driver car you have to complete each phase and have a drivable car at the end of each day, for a project car you can have 42 years (real number for a project car a friend of mine is working on) between starting and a drivable car - but phases are still things you complete in a few hours either way.
