There are loads of bonuses- feels important to say that first. When we all get on, and have great times there is NOTHING better.
However hardest bits-
Not having a second adult to counter or back up or intervene. Two kids, both have pretty intense emotions. One kicks off, the other usually follows suit . Having them both going off at once feels impossible. When they were little, post time with their dad they'd be all over the place and I'd find myself running between their bedrooms for hours trying to soothe away the crap he'd created for them and between them.
When they are sick. Not the worry as I don't really have anxieties there but the load and concern that if I go down we are buggered. Worse when both needed me to get them to school. Little one was being sick, couldn't take them on a school run.. sorting out getting the other to school was a panic..
Holidays - I am massively independent and happy to be single but holidays make me so sad... feels so alone being with the kids alone. There are families everywhere and I'm so aware of what the kids don't have with just me there on holiday. Neither get 1-2-1 time, we have to fit everything for all of us... I'm much better travelling alone totally
The cooking and meals. Oh my life I get fed up being the one responsible for working out what we can eat and keeping us all happy.
Finally bloody activities. Doing all the taxi-ing drives me nuts and really limits how much they can do.
Money goes without saying.