How do I downsize my stuff so I can move into a 40' Container house?

Take nothing more than what comfortably fits into the rooms...2-3 sets of bedding per bedroom. Two sets towels per person. Tallest armoires you own that will fit ceiling space and yet provide adequate walk space. Select books you wish to keep and sell or donate the remainder. Same for yard care items, children's belongings, toys, cleaning supplies, duplicate fans, vacuums, kichen equipment (additional sets of dishes/utensils/glassware), garage items. Pare collectables to absolute minimum.

Measure, measure, measure. Get an idea of how you want each room furnished, measure your existing furniture and make sure it will fit where you think you are going to use it in your new place, and only bring what will. Donate or sell everything that won't fit. As far as kitchen stuff, again only bring what will fit and only if you use it regularly. People may need 6 serving spoons (think holidays) but they sure don't need 6 cutting boards or food processors. You may also have craft supplies to downsize and/or organize. If you won't have room, you may have to donate/sell all of them. So keep that in mind when you are measuring your space for items to keep. It is time for hard choices (you really don't need those old, dried flowers you got from your high school crush anymore, or those boxes of greeting cards that you have received over the years.) If you do part with something you think you love, take a photo of it. It is not the same as keeping the item, but it sure will fit a lot better. Good Luck!

Only keep what you use in a week

The container is 40 feet long but how wide is it? Are there divisions inside? Are there kitchen/bathrooms in place? Are there cabinets in the kitchen bathrooms? How high is the interior? How many "rooms" are there? You need to know what you will have before you start to divest yourself of your possessions. Are there any outbuildings? Is there any closet space? Measure what is there and recognize what you have the talent and ability to create for storage. When you know exactly what you will have for room, then you can analyze what you do have now. Is every room in your house, inc. attic and basement and garage filled to overflowing? Then you will indeed need to get rid of things. Start doing that now, don't wait till moving time. Good luck, it will be challenging, but maybe you will have all the room you really need.

I would recommend reading the book " The magic art of tidying". It is amazing for figuring out how you should down size.

I would look at what other people have creatively done online.