Do a small area, to keep that area clean for a certain amount of time (maybe a wk). Then, do another small area, & try keeping both the areas you've done clean. Keep adding on slowly, so that you don't get overwhelmed.

Or clean one area a day, another the next etc. So you clean one little small space every day or every other day, but then it doesn't build up into you having to clean the entire room in one go.