I wasn't paying that much attention to geometry in high school. But I'm pretty sure it describes the nature of space. Specifically, that it can be measured and that you are bound by the shapes of things. So stop trying to cram so much stuff into your limited space!
You know that adage "A place for everything, and everything in its place"? I'll admit this has always sounded super anal to me, but in my quest for a calmer life I've begun to embrace it. Every single thing you own should have a designated home. Let’s just repeat that for emphasis: Every. Single. Thing. You. Own. Should. Have. A. Designated. Home.
It's pretty much impossible to tidy up your space if there is a large pile of things that don't really belong anywhere. They sit on counters and end up in stacks on the dining room table and every available chair, then start beckoning to other stuff to join them. The next thing you know you are wading through piles of clutter.
If you have dozens of items for which you can't find a home, it's likely because you don't actually have space for them: If your bookcase only holds 200 books and you have 250, you've got a problem. You will either have to get rid of 50 books or find another shelf. Piling those extra books in an artful stack on the floor is not really solving the problem. And don't you dare tell me you will buy more storage containers - that is not a solution, it's just a way to disguise your problem.
To be sure, there are lots of ways to be very clever about maximizing the space you do have. I highly recommend checking out Apartment Therapy if you haven't already. It's both crowd-sourced and curated, and you'll see fabulous examples of ingenious storage solutions. And you'll see gorgeous living spaces in which the occupants have opted for less.
Getting rid of the extra is the first, best way to find homes for your stuff. There is bound to be unused junk taking up precious real estate in your drawers and closets. Once you've cleared the decks, work on finding permanent places for the things you're keeping. Ideally, they will live very close to where they are used. You will find it's fairly easy to clean up quickly if you know where each thing goes... I swear!