I'm still trying to bring less, but it's getting hard! I recently had a 2 week stay and was mortified when I realized I needed to ask my client to help me bring in a bag of my portioned/frozen dinners I'd put together just for that stay. I didn't realize I couldn't lift it until I was trying to get settled in the house (my boyfriend had packed the truck for me).
I bring:
Coffee, creamer, a french press (I'm surprised how many people drink coffee but have no means of making it at home!)
Also I bring toilet paper, paper towels, laundry detergent if the stay is 3+ days, and all of my toiletries in travel containers. The laundry detergent lets me wash/re-wear clothes instead of having to bring more. I only bring enough to get me through 2 days, so on the third day, I wash.
My pillow, a blanket, and plenty of food/snacks for myself especially on long stays (on short stays, it's just easier to either run home for dinner or grab a bite nearby). Beyond that, like Deb said, layers, phone, charger, laptop, etc.