Clutter: Stuff you do not use....ever....at all. Stuff you shove back on the shelf or in the drawer. Stuff that doesen't fit...you, your lifestyle or your decor. Stuff someone has given you that you feel obligated to keep. Stuff that reminds you of a person, trip, evening, event or activity that you enjoyed. Stuff that you might need.....someday.
There's "good stuff", then there's the rest. You need to get rid of the rest!
Why do you need to de-clutter?
1) So you can lighten your load
2) Easier to clean
3) See what you do have and enjoy the view!
4) So your children won't have to deal with it
5) So someone else can enjoy (your stuff is someone else's treasure)
6) To evaluate what is necessary
I am sure there are many more good reasons to de-clutter. You will probably have to de-clutter more than once since this activity is actually a character-building exercise which requires practice and fortitude (endurance). You must have a sense of humor too!