There's no universal rulebook for being a parent. Sure, there is an endless deluge of books about parenting, but among them, you'll find an equally endless deluge of contradictions. Everyone has their own method of parenting, and everyone has their own rules. For example, some parents don't let their kids have sugar, and some parents are… normal. There are hardly any hard and fast rules about raising kids, except for maybe don't let them play with knives unattended. Other than that, it's up to you. This means that there are hundreds of thousands of parenting choices you have to make every single day. So beyond the lack of sleep, no wonder it's exhausting. Parenting is a complicated business, and decisions make you tired.
That's why, when you have a minute to yourself, maybe on the toilet, maybe right before you close your eyes, it's nice to read some tweets that understand your struggle.