Second this, all the thinking and planning in the world often pales compared to: Sit down where you need to do the work / Open the tool you need to do the work

Second this, all the thinking and planning in the world often pales compared to: Sit down where you need to do the work / Open the tool you need to do the work / Do the work. I don't program, but I paint / illustrate outside of my day job and the only way I've ever, ever gotten over the 80% hump is to just physically be where I need to be and force a handful of actions to get moving. Also, resetting the "done" point is important - sometimes you're lagging because you've actually finished, you just need to call it, clean it up and ship it, even if it means sacrificing some of the ideals / nice to haves you had planned.