Be logical with packing. Don't try to declutter as you pack, throw anything obvious away but don't stress,just shove it all in a box, you can throw anything away that doesn't find a home as you unpack again.
Pick a room that you don't use much, pack it then go round and pack anything you don't need. Books off bookshelves, summer clothes etc and move them in to the box room.
Label all boxes with contents and the room they need to go in.
As you get to the last couple of days pack a suitcase as though youwere going on holiday for a couple of days. That will be what you will need to remain unpacked. Pack anothger one to have things the first couple of days (change of clothes, soap, book, toys). Pack a box with the kettle, mugs, cereals, a plate, bowl, knife, fork and spoon each and washing up stuff and keep to one side. Make a dish of lasagne, cottage pie or something to bung in the oven the first night. Everything else can now be packed. One room at a time, all in boxes.
You should now have one room with the bulk of the unused stuff in which can go straight in the spare room/loft to be dealt with last. All the rest of your stuff which you use should be in boxes in the room inwhich it lives ready to be placed in the equivalent room of your new house and unpacked.
Voila!
Ds is not yet 3 and has lived in 5 houses, I've done this a lot!