The bad:
You have all the responsibility, all of the time.
Need a pint of milk because you forgot to buy some earlier from the corner shop at 8pm?
Get the kids up & dressed then, because there is nobody there to watch them while you pop out for 5 minutes, or go without until you can get some in the morning.
There is never anyone to give you those 5 minutes, whatever you need them for because the only time anyone else is in the house they are visiting.
They may help a bit for a while after you become a single parent but it won't last until your kids are grown.
Sometimes, you really need 5 minutes.
I have some neighbours who are seperated & she has to put up with screaming matches on the doorstep with him about once a week.
You may have that kind of embarrassment to deal with.
Sooner or later you'll have to face up to the fact that you are alone & that it is different from being alone without kids.
You can't go out without difficulty, if you get drunk there is nobody else who will watch the kids if they need you, if you are sick you'll have to deal.
Even if you are glad you've separated, you'll still feel sad about it sometimes.
Awkward relationships with joint friends, some married ones may now assume you want their man (even if he's as undesirable as can be) or no longer include you in things you did as a couple.
See something beautiful, funny, or got some great news?
There is nobody to tell who is special to you.
Christmas presents... your pile will look small to nonexistant, same goes for mothers day, birthday etc.. as there is nobody to help the kids get you a card.
Finding a babysitter (unless you already have one)
Finances maybe - turns out my ex was spending 90 percent of our income so I am actually better off.
You'll have to deal with your own DIY or other jobs he currently does.
You'll also be the one to deal with the 'where's daddy?'/'why doesn't he live here?' etc.. fallout as well as the 'I miss daddy' stuff.
You may have to see your ex with another woman & when your money is tight you may find it hard to remember he's spending his money on her - it's not yours because you are not a couple anymore.
You'll have to deal with how he reacts too..
He may be a great single dad & have them at his house, be civil etc..., or he may disappear & never be heard from again, or anything in between.
Even if he's great, you're likely to be their primary carer so you'll have to be super careful not to blame him for stuff.
Making your kids dislike him might seem fine when you've had a bad day, but it will come back to bite you when they are older so don't do it.
You will also have to deal with the fallout as regards grandparents etc.. if they are part of your kids lives.
His parents will almost certainly see you as the bad guy, but it's important for your kids to have relationships with both sides of their family if possible & you'll almost certainly have to sort that.
He might be better without you.
You'll have to deal with that, someone will be horrible enough to point it out.
But the good:
You have all of the responsibility, all of the time.
The money you have is in your control.
There may be less of it, but you can make a plan then stick to it as there is nobody else to mess it up.
Never sit in the front room pretending you enjoy Top Gear again, or miss the best bit of the film because he talks over it/asks you what's happening etc...
Control of the remote is yours!
That friend of yours he doesn't like? You can invite them round whenever you want.
Feel like spending the evening on the phone to your sister/friend/whoever? Go ahead, you get to decide & there's nobody to stop you.
Wear what you want/do your hair how you want/try out new makeup.
He won't be there to disapprove, tell you that style doesn't suit you etc..
Feel free to run round your home with your knickers on your head if you want, it's your home.
All the wardrobe space is yours.
Move the house round as you please or put up a fireman calendar in the kitchen - you now have total control & don't need to refer to anyone else.
The toilet seat stays where you put it as long as you teach your kids to put it back that way.
You'll spend a lot less on food- you may have to learn to buy less because you'll have a habit of making meals that include feeding your ex.
Sleep better because you aren't back to back with someone you have just been arguing with, breathing in that ill will as you drift off.
If one of your kids is crying their eyes out, you'll be dealing with them, not worrying about his reaction if they don't stop.
Happier kids if the atmosphere is better.
There may be kids in it now, but you have your life back under your control and once you get used to it, you may never want to be part of a couple again in case you lose it.
Google places to go, check local papers, the tourist centre, council, ask mums at the school etc.. to find cheap places to take your kids.
Some places offer discounts for local people or single parents if they go on certain days. Others may be free for under 2s/3s/5s or even adults.
I spent £10 (the cost of a day ticket) and got a years free admission to my local aquarium for me & my son. We can go everyday if we want & they have a play area with a great big indoor climbing frame/ball pit beside their cafe which is free to use
My local zoo has cheap rates for single parents on Tuesdays.
Find out if they are places you can take a picnic, then you can set your budget accordingly.
You can plan these things & carry them out, because it's just you.
It's hard, especially at times like 00.01 Jan 1st when you can hear what seems like the rest of the world out celebrating a new year while you are home alone with the kids, but if being a single parent is what has to be, it can also be wonderful.