Moving is probably the best opportunity to reevaluate everything you have — you're already going through all your stuff anyway. Depending on the type of move and your packing style, though, the decluttering and discarding will happen before the boxes are closed or once they've been cut open.
Personally, I avoid stress by pacing myself and start packing a few weeks before a move, which includes trying to declutter as much as I can as I go along. Why would I want to lug around a bunch of extra stuff? On the other hand, now that I am moving to a bigger place (a first!), I've found more items that I'm not sure about discarding. My fiance is definitely in the "do it after" camp, because he just wants to finish packing as quickly as possible.
What's your packing style — do you declutter and discard before or after?
Image: Laure Joliet