Which approach is most effective for you?

Let's say you have 3 giant couches & you've washed all the slipcovers, linings AND cushion parts. Putting them together is a tedious, difficult chore. Do you:

1) Bull through & get the whole thing done, even though it takes 2 hours & you break 2 nails & can barely lift your arms afterward?
2) Just pick at it over the course of a couple days, knowing it will get done eventually?

I washed all these things on Oct. 7 in advance of my b'friend's visit. He helped put the frame covers on but then I bogged down because I needed to repair some of the cushion linings. Last night I decided to tackle the project just in case I felt like straightening up the house enough for Christmas decorations. And finished settling the last cushion just now. Helllooooooo, December Third!

I use my timer a lot for 'don't wannnnnnnnnnna!' chores but am not sure whether to rely on the baby-steps rule or just grit my teeth.