Marie Kondo's only criterion for keeping anything is whether "the item sparks joy." Her method for uncluttering your home (and your life) has become internationally known through her book "the life-changing magic of tidying up." Kondo's approach to tidying your home promises a whole new mindset once you have gone through her radical process of ridding yourself of everything that doesn't make you feel good. And organizing, she makes clear, cannot start until you have gotten rid of all that excess stuff. She also promises no relapses because your mind will have shifted during this radical process.
Take your wardrobe for example. You probably have a bunch of items in the back of your closet you haven't worn in years but keep around because you might just sometime feel like wearing them again. Or maybe you feel guilty about getting rid of them because you think that's wasteful (well, think consignment store). But if you do take the time to take each piece into your hands and reflect on whether this piece of clothing makes you feel good when you wear it (Kondo's method), and the answer is a resounding "nahhh, not really," you know what to do. Get rid of it. Same advice goes for your books, nicknacks, pantry and everything else in your house.
I think it's worth a try. Although my home is not cluttered I know I keep things around that wouldn't pass muster if I asked myself that test question. Kondo's idea behind all of this radical purging is to only surround yourself with things you love and to clear stuck and stale energy in the process, inside and out. See this previous post on clutter inside/clutter outside.