When I meet with my sellers at the beginning of the process, I advise them to clean and purge before they list if they can. This helps to clear out the home and make it easier for potential buyers to envision themselves there. Purging also gives them a big advantage as they start the packing process. As they clean and purge they can also start packing away items they won't need in the near future. Then, when we list the home is clean, decluttered and sellers won't have such an overwhelming job once we get under contract!
If weather permits, host a garage sale as part of your purge or sell some bigger items online with the goal of purchasing some new items for your new home. That will make all the hard work feel worth it!
Once we are under contract and the big packing job starts, work room by room packing up everything except with the necessities and leave a box or two open so that on moving day you can add the everyday items and tape them up and load them in the moving truck to take to your new home.