Love retreats.
Packing: first I look at the amount of space I'll have to myself, including storage space. And I look at the amount of space I'll have in the vehicle. Do I have to carry everything, especially up stairs? Will my rolling cases get to the sewing spot? What's the electrical situation in the facility? What is the retreat providing? Ironing equipment? Type chairs provided? Lighting in the room? How long is the retreat? 1-5days?
What project to take? If a workshop, there will be a supply list. I choose a project, I can do mindlessly, so I can talk, sew, get distracted, stop in the middle, go on a shopping trip. And I take several projects that require similar equipment. I get hot, so I take a fan. A sealable mug. Lights. Seating: either my office chair or cushions. A special small table to get my machine down to standard table height. Power strip and extension cord. Pin cushion with trash bag attached. Box of usual sewing tools. Cutting equipment. Cutting mat/iron surface combo. Wand iron tool-takes very little wattage. Thread. Chap stick. Finger nail file.
I'll have to think some more. Making a list would help.