My family of 5 lives in a 3 bedroom house. So my 2 daughters share a room, and have since my 12 year old daughter was born.
Family is about more than stuff. It’s about being part of something bigger. Sharing is a big part of that. We share our time, our possessions, our love, our concerns, our space.
So when my son goes off to college in a year, I’m absolutely OK with one of my daughters using his room while he’s away. And he will be too. Seriously-- are they supposed to share a room when there’s an empty bedroom down the hall? I’m supposed to heat an empty room when there are other members of my family that could use it?? That’s not how my family-- or I suspect the OP’s family --really operates. A bedroom is a room in our family’s house. It’s not a shrine. Of course it will be there for my son when he returns-- and whoever has been sleeping there will change the sheets and vacuum the room before he gets back home.
Seriously-- you’re afraid they’ll use your nail polish??? You get to go away to college, and you’re afraid they’ll use your $5 bottle of nail polish? I have bad news for you: any you leave behind is likely to be dried out by the time you get back anyway. So why not make a gift of all that nail polish to your younger sisters?? You don’t think that concerns like this are reading a little petty?? Nail polish???
Your clothes: I grew up with 3 sisters, and through those years we were all the same size. We shared clothes. The rule was that you couldn’t wear someone else’s stuff if the tags were still on it, or if they had set it aside for imminent use. Otherwise, it was fair game. (In fact, as each of us moved out, we saw a whole part of our wardrobe disappear. First one… there went the good jeans. Second one… there went all the professional clothes/ suits. And so on.)
Would you really begrudge your sisters the use of your blue sweatshirt that would otherwise be home in a drawer??? I assume that if they’re close enough to your size to actually wear your stuff, then they’re old enough to care for it properly. If not, then use these last weeks showing them how to do laundry.
Have your sisters made a habit of trashing your stuff? If not, then why are you assuming they’ll do so the minute you leave the house? Your guitar has made it this far- I think you can probably assume it will survive your time in college unscathed.
I think you do have a right to expect that your journals will remain unread. So do as others have suggested-- invest in a lock box, tell your parents what you’re doing, and ask where they want you to put it-- will the garage be OK? Or the attic? Or the basement?
I’m no psychologist, but I suspect this post isn’t about your room or your stuff. I suspect that you’re starting to get really nervous about heading off to school, and you want everything to stay exactly as it is right now. You want to return home to the same house, with everything in the same place, all your local relationships exactly as they are now. And you know in your gut that it’s unlikely to happen. People will grow and change, and you won’t be there to see it happen. And that’s OK-- you’ll be growing and changing too, and it will be OK.