Make a list of outside service people to call, such as rug and upholstery cleaners, window washers, floor polishers, etc. Schedule time to work on each project. Do not feel you have to finish one room in a day. Each cleaning session should be at least 3 hours. You don't want to burn yourself out, but you do want to see some results.
Progress is very motivating.
Make sure you have plenty of supplies on hand. You don't want to have to abandon your project because you ran out of garbage bags, cartons or cleaning supplies. When clearing storage areas, be honest. When cleaning any cluttered area, make decisions. The clutter got there because you delayed making a decision.