If you find that you need to move your stuff before you move yourself, don't fret; arrange for your belongings to be warehoused at your destination. Many moving services also offer warehousing services, so they can keep your items safe for you when you can't make it quite yet.
It happens: you start to move into your snazzy new place, and your stuff doesn't fit. Your options are to have a quickie garage sale, or put your extras in storage. If you don't need the money, check out storage warehouses for your overflow. They're inexpensive, and it's better than selling your stuff for next to nothing.