The biggest obstacle to me is me. Aside from going into a lot of notes on this, all I can say is that procrastination and daily chances at resistance in my work all come down to me.
Sometimes it's good to punt on one project in favour of another. If something isn't working it isn't working and it's best to set it aside and work on something else.
Stop working when concentration is on the wane. But come back refreshed at some other time to continue working.
At some point I have to decide that what I've written will suffice.