One of my biggest productivity hacks is that for some projects I'm willing to park my ass in a chair for eight hours and accept that the project will happen as it wants to, as long as I don't force it.
It's liberating to accept that sometimes your "work process" involves spending hours alternating between writing tricky passages and laughing at YouTube videos.
When I try the alternative--that is, disciplined, focused work--it's a dice roll at best, with five of the faces turning up "procrastination."
The big projects go smooth if you can just un-clench and let them happen how they're meant to. Doesn't look good on a time card, but that slow, relaxed approach has, in the past, saved me days that would have been spent delaying, replacing them instead with hours spent goofing off.