1. The couple of weeks before you make your move, where you sort what you need and what you don't need, so you can get rid of the latter.
2. A few weeks/months after you move, when you realize you only use 25% of what you kept and purge once again.
After that, it's really quite pleasant. The biggest change is spending more time out of the house in public spaces, since you no longer have the space to maintain separated individual little worlds in your home.
My living room is a quarter full of shipping supplies for selling my things on eBay, and I am getting sick of it. It's not even that I want the money, but that I don't want to just toss things in the landfill.
How do you fit furniture into a garbage chute?
The correct way to get rid of any garbage that I can't fit into the garbage chute is to take it to the dump (which is a bit tricky without a car).
The opposite happens too, when you realize that you actually need a tool or an adapter that you just gave away, and they're actually quite expensive!!
But small is good for students or bachelors indeed, because as he said he's not often home, and he doesn't need to have separate rooms to isolate himself from family members and get some "alone" time.
When you get kids, that's a different story.