I wish I'd understood the degree to which small children destroy you. The amount of focus time you get falls by 90%+, you sleep horribly every night without fail, and you spend every quiet moment waiting for one of them to start screaming because they found some new and ingenious way to hurt themself.
Maybe a lot of that was having a 1-3 and 3-5 year old wfh during covid, but I feel like I'm broken ever since.