It may not have occurred to you, but if you don't declutter regularly, it is likely that you don't need - or even want - everything that is currently in your house. Even for people with conservative shopping habits, it is very possible that the amount of stuff coming in significantly exceeds the amount of stuff going out each week.
Don't believe me? Try this exercise: For one week, keep track of everything that comes into your house (other than consumables like food and toiletries), as well as everything that goes out. After keeping a list for just a week or two, you'll quickly see why stuff accumulates continually in your home, making the space feel smaller and more disorganized over time.
So next time you start an organizing project, declutter first and organize second! And if you want a little guidance, I'm happy to help. Contact me on the contact page or at firstname.lastname@example.org.