Dealing with the debris

TL;DR When you tackle an extremely messy living-space, a great place to start is dealing with the debris. Debris here means anything that does not belong in the space in the first place, the big three being (1) Trash, (2) Laundry, and (3) Dishes. One helpful technique is choosing a small task and setting that as an intention, e.g. "I will gather the laundry". Then you can stay on track by repeating a laundry-mantra or singing a laundry-song.