You can do this. I'm going to make some suggestions. I am not going to suggest Marie Kondoing, Fly Ladying or any other brandname.
Start with the bathroom.
You need a bin bag/carrier bag, a manky towel torn into pieces, hot water and soap - any kind, even shampoo will do - and 10-15 minutes.
Go into the bathroom. Take everything off the surfaces. Chuck everything that isn't usable into the bag. Tie the bag up and put it outside the door.
Run the hot tap. Make one of the pieces of towel wet and squeeze out. Rub your chosen soap into it. Clean the bath. Doesn't matter if it isn't perfectly shiny white, you're getting dust, dirt and suchlike off. Rinse out the towel as often as you need to. Five minutes, tops.
Do the same to the windowsill. By now, the water should be looking filthy. Drain, rinse the cloth and refill it. If you feel up to it, wipe over the windowframe and glass, then rinse/wipe off the windowsill.
That cloth is probably looking manky. More hot water and go over the outside of the toilet (a huge dust and dirt collector). Chuck that piece of towel.
Clean bit of towel. Go over the outside of any cupboard, shelving, and then the skirting boards. If you can be arsed, go over the floor quickly, rinse the cloth out, empty the sink, wipe quickly over it and the taps and you're done.
You can worry about tiles, walls or doorframes another day. It's time for a rest/bath in a much cleaner bathroom than you had around fifteen minutes ago. Put the binbag/carrier by the front door, take it out when you leave tomorrow and put in the wheelie bin.
The next day - fifteen minutes in the kitchen. Find a spot. Doesn't matter what one, just needs to be about the size/area of a microwave oven. Clear it (including chucking anything rubbish related) and wipe over it. Do the same dump-crud-on-your-way-out-the-door in the morning.
Day 3. Do you want to do another spot in the kitchen? Nobody's going to arrest you for chucking out chipped plates or mugs. Life's too short. Have another bath, giving the sink a quick wipeover whilst it's filling.
Day 4. Do you need to do some washing? Clear off the crud from on top of the machine and do the hot water and soap thing over the top, front and inside the door, including the seal. You will probably want to chuck whatever you use to clean the seal. That's fine. Then chuck the washload in, set and have a rest.
Day 5. It's been a long week. Wipe over the sink, perhaps chuck a few bits away in the kitchen whilst food is cooking. Don't worry about the rest.
Day 6. This is for you. Strip the bed and bung the sheets into the WM on a hot wash. Go and sit on your bed and, without getting up, chuck random things into a carrier bag, tie and chuck out.
You don't need to carefully sort through crap to see whether something causes you joy, just get rid of anything that isn't 100% essential to your current functioning. It's cluttering up your mind, house and heart.
If you want, hurl dirty clothes in the general direction of the washing basket. Or step over them, you can deal with them later if you feel like it. Have a cuppa and sit down.
If you have a tumble drier, that's brilliant. Put your bedlinen through it and, whilst it's still hot, go and make your bed.
You're done attacking The Mess for the day. Just get on with the usual stuff. That's enough (but you could chuck another bag away in the kitchen or clean another small patch whilst food is cooking - purely optional, though).
Day 7. You've woken up in a clean bed. Enjoy it. Later, you could take some of the clothes down to the WM, but you've got time to breathe in the smell of the bedlinen right now.
Day 8. Let's make sure your room is nicer. Get stuff off the floor, wipe the windowsill and vacuum. Hopefully, you've been paid by now and have some flea spray. Open the window a bit and spray into the corners. Your room is going to be beastie free tonight.
Day 9. Quick wipe over the bathroom - it's going to be much easier than the first time, as it's pretty much just the sink, bath and top of the loo that needs doing. Quick bit of cleaning in another patch in the kitchen.
Day 10. Bug spray the living room after vacuuming it. If you can, wipe over the windowsill first. That'll keep teens out of there and in their rooms. They can collect a bin bag of rubbish whilst they are in there.
Day 11. Hallway. How many coats do you need? Bet nobody wears the others. They don't belong there - the owners have them upstairs, even if they are only going to leave them on the floor. Chuck out any obvious rubbish and vacuum. Then flea spray.
Day 12. Probably better have a look at the hob/cooker. Hot water, damp cloths, soap. It'll be gross, so a scratchy sponger will help if you have them (about 50p for a load of them). Get the worst off and wipe dry.
Day 13. Wipe over the bathroom, chuck some more stuff out from the kitchen, clean another patch. How about the windowsill/back of the sink? That collects dead flies and cobwebs.
Day 14. How are you doing? Can you see how much difference you've made in 15 minutes a time? It's about time the teens did something with their rooms. But if they don't, it's their problem, as you are dealing brilliantly with your own areas.
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Lots of us say our homes are dirty when we actually mean they are untidy. Reduce the untidiness (by chucking stuff out) and you have space to clean.
I use a different logic than most for tidying - if there was a fire,
would 'this' be Fuel?
Would I trip over it as I escape?
Would I insist upon taking it with me?
Would I have to replace it within 24 hours? A Week? A Month?
Would I always cry if I didn't have it anymore because it had been burned to a pile of ash?
- that helps me be realistic whether it's something that's worth the bother of finding it a home or trying to fix it (clue: chances are it isn't fixable, so don't waste your valuable time, energy and emotions on it).
If you do actually mean it is dirty, rather than it's too untidy to clean, then you've got a head start, as all you have to do is clean.
You can do this. [Hug]